Ask questions which are clear, concise and easy to understand.

My doubt is to the institution/dignitaries of myCBSEguide. I am a student studying in class 9. I am too much worried about the consumption of time I take for attending 1,2,3,4, and 5 marks questions . Usually I takes 1/2 sheets for attending 3,4 and 5 marks questions. My teachers advices me I am writing too much than the limit. But,unfortunately I could't control my writing. By doing so I miss so many questions which I know. The board exams are nearer to me. So, respected dignitaries please send me how to manage time and how much  to write in my exams.

Posted by Vaishak Kurup (Jan 19, 2017) (Question ID: 1475)

2,3,4,4,2x+1,5,5,6,7 find x and mean by imperical formula

Posted by Daksh Bhagat (Jan 19, 2017) (Question ID: 1470)

  • Incomplete question

    Posted by Rashmi Bajpayee (Jan 19, 2017)
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The curved surface area of cone is 550cm²and the height of cone is 24cm. Find volume.

Posted by nimisha singhal (Jan 19, 2017) (Question ID: 1469)

  • Answers:
  • Let Radius of Cone is r and slant height is l.

    height of Cone (h) = 24 cm

    CSA of cone = 550 cm2

    We know, 

    l = r2+ h2

    => l = r2+ 576           ............(1)


    CSA = π×r×l

    => 550 = 227×r × r2 +576

    Squaring both side,

    => 302500 = 484 r2 (r2 + 576)49

    => 30625 = r4 + 576r2

    =>  r4 + 576r2 - 30625 = 0

    Put r2 = t

    =>  t2 + 576t - 30625 = 0

    =>  t2 + 625t - 49t - 30625 = 0

    =>  t(t + 625) -49(t+ 625) = 0

    =>  (t + 625) (t-49) = 0

    => t + 625  = 0 or t-49 = 0

    => t = - 625 0r t = 49 

    => r = -625 is not possible so r2 = 49 

    => r = 7 

    put in (1), we get 

    l = 49+576

    => l = 625

    => l = 25

    =>Volume of Cone = 13πr2h

    => Volume of Cone = 1×22×49×243×7

    => Volume = 1232cm3


    Answered by Naveen Sharma (Jan 19, 2017)
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What is disease and define it's types 

Posted by Simranvir Sondhi (Jan 19, 2017) (Question ID: 1462)

  • Answers:
  • In Simple words disease is as name word itself suggests without ease.

    Disease is an abnormal condition of a part, organ, or system of an organism resulting from various causes, such as infection, inflammation, environmental factors, or genetic defect, and characterized by an identifiable group of signs, symptoms, or both.

    <font face="Arial">Types of Diseases</font>

    <font face="Arial">•</font>  <font face="Arial">Acute diseases</font>

    <font face="Arial">-</font>  <font face="Arial">The symptoms appear suddenly.</font>

    <font face="Arial">-</font>  <font face="Arial">These diseases are short term ie the symptoms last for short period of time.</font>

    <font face="Arial">-</font>  <font face="Arial">Eg. Influenza (Flu) , Common cold.</font>

    <font face="Arial">• Chronic diseases</font>

    <font face="Arial">-</font>  <font face="Arial">These diseases long term diseases.</font>

    <font face="Arial">-</font>  <font face="Arial">Their symptoms develop gradually and are long lasting.</font>

    <font face="Arial">-</font>  <font face="Arial">Eg. TB, Cancer etc</font>

    <font face="Arial">• Congenital diseases</font>

    <font face="Arial">-</font>  <font face="Arial">These are inborn diseases i.e. present from birth.</font>

    <font face="Arial">-</font>  <font face="Arial">Most of the diseases are permanent and generally not easily curable.</font>

    <font face="Arial">-</font>  <font face="Arial">They could be due to genetic abnormality or metabolic disorder.</font>

    <font face="Arial">-</font>  <font face="Arial">Eg. Down syndrome, Hemophilia, colour blindness, Sickle cell anaemia etc</font>

    <font face="Arial">• Acquired diseases</font>

    <font face="Arial">-</font>  <font face="Arial">The diseases which a person gets in his or her life time (i.e. after birth) are called acquired diseases.</font>

    <font face="Arial">-</font>  <font face="Arial">Acquired diseases are classified in to two categories</font>

    <font face="Arial">1)</font>  <font face="Arial">Communicable diseases (Infectious diseases)</font>

    <font face="Arial">2)</font>  <font face="Arial">Non-communicable diseases (Non-infectious diseases)</font>

    <font face="Arial">1) Communicable Diseases</font>

    <font face="Arial">•</font>  <font face="Arial">Communicable diseases are caused by pathogens such as virus, bacteria, protozoan, worms or fungi.</font>

    <font face="Arial">•</font>  <font face="Arial">The organism causing the disease may be transmitted from an infected person to another by means of air, water, food, physical contact or insects (vectors).</font>

    <font face="Arial">•</font>  <font face="Arial">Communicable diseases can be further classified on the basis of the causative agents like Bacterial diseases, Viral diseases, Helminth diseases, Fungal diseases etc.</font>

    <font face="Arial">2) Non-Communicable Diseases</font>

    <font face="Arial">•</font>  <font face="Arial">These are non infectious diseases ie do not spread from an infected person to other healthy person</font>

    <font face="Arial">•</font>  <font face="Arial">These diseases include deficiency diseases, degenerative diseases, cancer etc.</font>

    Answered by Naveen Sharma (Jan 19, 2017)
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The probability of guessing the correct answer to a certain question is x/2 (x upon 2). If the probability of not guessing the correct answer to the question is 2/3 ( 2 upon 3) , then find x.

Posted by Arish Faraz (Jan 18, 2017) (Question ID: 1447)

  • Answers:
  • Ans. Let A denote the probability of guessing correct answer and B denote the probability of not guessing correct answer.

    Then, pA = x2 and pB = 23

     pA +pB = 1

    => x2+ 23 = 1

    => x2 = 1 - 23

    => x2 = 13

    => x = 23

    Answered by Naveen Sharma (Jan 18, 2017)
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Bhor's atomic model

Posted by NITIN KUMAR (Jan 17, 2017) (Question ID: 1435)

  • Answers:

    In 1913 Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus. The motion of the electrons in the Rutherford model was unstable because, according to classical mechanics and electromagnetic theory, any charged particle moving on a curved path emits electromagnetic radiation; thus, the electrons would lose energy and spiral into the nucleus. To remedy the stability problem, Bohr modified the Rutherford model by requiring that the electrons move in orbits of fixed size and energy. The energy of an electron depends on the size of the orbit and is lower for smaller orbits. Radiation can occur only when the electron jumps from one orbit to another. The atom will be completely stable in the state with the smallest orbit, since there is no orbit of lower energy into which the electron can jump.


    Answered by Naveen Sharma (Jan 17, 2017)
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How can we define sound?

Posted by Ashish Sharma (Jan 17, 2017) (Question ID: 1427)

  • Answers:
  • Sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a transmission medium such as air or water.

    Answered by Payal Singh (Jan 17, 2017)
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  • Vibrations that travel through the air or another medium and can be heard when they reach a person's or animal's ear.

    Answered by Naveen Sharma (Jan 17, 2017)
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What is molar mass


Posted by Abhisek Yadav (Jan 16, 2017) (Question ID: 1409)

  • Molar mass is the amount of mass in one mole of a substance. A mole is used in chemistry as a counting unit indicating the amount of ions, atoms, molecules or formula units in a specific chemical sampl

    Posted by Payal Singh (Jan 17, 2017)
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  • Answers:
  • The mass of one mole of the substance is called molar mass of that substance. Its units are g/mol. If the substance is atomic, its molar mass is equal to gram atomic mass. If the substance is molecular, its molar mass is equal to gram molecular mass.

    Molar mass of magnesium (Mg)= 24g/mol

    Molar mass of oxygen (O2)= 2x16= 32g/mol

    Answered by Shweta Gulati (Jan 16, 2017)
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Name the three organs of the government

Posted by Akhil Gupta (Jan 16, 2017) (Question ID: 1397)

  • Answers:
  • The three main organs of the government includes executive branch,legislature branch and the judiciary branch.

    Answered by shruti dadhwal (Jan 16, 2017)
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  • Three main organs of Government

    1) Legislature 2) Executive 3) Judiciary

    Answered by Naveen Sharma (Jan 16, 2017)
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There are how many members in Look shaba

Posted by Varsha Panchal (Jan 15, 2017) (Question ID: 1388)

  • It is Lok shaba

    Posted by Varsha Panchal (Jan 15, 2017)
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  • Answers:
  • There are 545 members in 16th Lok Sabha. 543 are elected and 2 are nominated. 

    Answered by Naveen Sharma (Jan 16, 2017)
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  • 543

    Answered by raman SINGH (Jan 15, 2017)
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what is circumcentre

Posted by Shankar Kapoor (Jan 15, 2017) (Question ID: 1387)

  • Answers:
  • Circumcentre is the point of intersection of three perpendicular bisectors

    Answered by raman SINGH (Jan 15, 2017)
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Why judiciary enjoys high level of confidence among the people?

Posted by Varsha Panchal (Jan 15, 2017) (Question ID: 1381)

  • Answers:
  • Judiciary is the most powerful weapon of the constitution of a country. The supreme court and the high court have the power to interpret any law of legislature or any action of executive. Judiciary stops the misuse of the governments power in making and with reference to PIL if any person is hurt by any law or action can file a PIL in the court against it.

    Some reasons because of judiciary enjoy highest level of confidence among the public.

    1)  Judiciary is independent and powerful in democracies. All the courts at different levels in a country put together is called Judiciary. 
    2) The Supreme Court controls the judicial administration in the country. The powers and the independence of Indian Judiciary allow it to act as guardian of Fundamental Rights
    3)  Citizens have the right to approach the courts to seek remedy in case of any violation of their rights. 
    4)  The courts also intervene to prevent the misuse of government’s power to make decisions. 

    5)  In the recent years, courts have given several judgments and directives to protect public interests and human rights

    Answered by Naveen Sharma (Jan 15, 2017)
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A stone of mass 4gm is to be thrown into a well. The sound is to be heard after 4sec .find the depth of well if (g=10m/s2)and speed of sound is 340m/s.

Posted by Kd Solanky (Jan 14, 2017) (Question ID: 1369)

  • Answers:
  • For the 1st part the stone is falling under gravity. Let t1 be the time from release to splashdown.

    d =depth

    So d= gt12/2  -  (1)

    After splashdown the sound travels back up. Using 330m/s for the speed of sound this gives:

    d=330×t2  (2)

    We also know that:

    t1+t2=4s  (3)

    Combining (1)and(2) we get:

    330t2= gt12/2

    From (3)⇒






    Solving this quadratic equation using Discriminant formula and ignoring the -ve root we get


    So t2=4−3.78=0.22s

    So d=330×t2=330×0.22=72.6m

    Answered by Shweta Gulati (Jan 17, 2017)
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  • this is 19h85 instead of 19h5

    Answered by Naveen Sharma (Jan 16, 2017)
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  • Ans. Let Depth of Well = h 

    tstone + tsound = 4            .................. (1)

    For  tstone (free-falling body ) :

    h = 12gt2=> t = 2hg

    tstone= 2h10

    = > tstone = h5

    For tsound (uniform motion): 

    h = ut=> t = hu

    tsound = h340

    Put Both values  values in eq (1), We get 

    h5 + h340 = 4

    => h5 = 4 - h340

    Squaring both sides

    h5 = 16 + h23402 - 2h85

    => h2115600 + 16 = h5 + 2h85

    => h2115600  - 19h5  + 16 = 0 

    Solve for h and you ll have answer

    Answered by Naveen Sharma (Jan 16, 2017)
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what do you understand by text orientation

Posted by Navdeep Yadav (Jan 13, 2017) (Question ID: 1344)

  • Answers:
  • It essentially is the means of how you want to view your text messages.

    This can be horizontally or vertically displayed on the screen of your Computer.

    Answered by Naveen Sharma (Jan 13, 2017)
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A rectangular tank measuring 5m * 4.5m * 2.1m is dug in the centre of the field measuring 13.5m * 2.5m. The earth dug out is spread evenly over the remaining portion of the field. How much is the level of the field raised?

Posted by Anusha Arora (Jan 13, 2017) (Question ID: 1342)

  • How can you dug a tank of width 4.5 m in field of width 2.5 m ?

    Posted by Naveen Sharma (Jan 13, 2017)
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  • Answers:
  • Area of field=13:5×2:5=33:75

    Upper area of tank=5×4:5=22:5

    Area of field on which soil is spread=33:75_22:5

    =11:25m   Volume of tank=5×4:5×2:1=47:25m^3

    Raised in level=volume of tank/area of field on which

    soil spread=47:25/11:25=4:2

    So,raised  level=4:2m


    Answered by Ghanshyam Kumar (Jan 14, 2017)
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Can you tell me the solutions of OTBA material hindi 2016 


Posted by Anuj Porwal (Jan 13, 2017) (Question ID: 1335)

  • Answers:
  • you can downoad it from here

    Answered by Vikrant Singh (Jan 14, 2017)
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Find the energy in kilowatt hours consumed by a machine of power 500watts? 


Posted by Archi tiwari (Jan 12, 2017) (Question ID: 1327)

  • Answers:
  • We know 1 Kw = 1000W

    Power of machine in Kw:  500/1000  = 1/2 Kw

    Power consumption in 1 hour = 1/2 * 1 = 1/2Kwh


    Answered by Naveen Sharma (Jan 13, 2017)
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0.18 grams of glucose contains how many atoms

Posted by SUNITHA D (Jan 12, 2017) (Question ID: 1325)

  • Answers:
  • So, glucose's molecular formula is C6H12O6, which means that every molecule of glucose contains Six carbon atoms ,Twelve hydrogen atoms, Six oxygen atoms.

    Molar mass of C = 12 g mol-1

    Molar mass of H = 1 g mol-1 

    Molar mass of O = 12 g mol-1 

    There fore,

    Molar mass of C6H12O6=(6x12) + (12x1) + (6x16) = 72 + 12 + 96 = 180 g mol-1

    Now we can calculate the number of moles of glucose as follows: 

    The number of moles of glucoses n  = w/M , where w is weight in gram and M is molar mass.

    => 0.18/180 = 10-3 moles

    It is also possible to get the number of atoms in the given sample by multiplying the number of moles with Avogadro number, NA 


    the number of atoms = n.NA, Where NA = 6.022 x 1023

    In above glucose sample, 

    the no. of glucose atomes  = 10-3 x 6.022 x 1023 = 6.022 x 1020 



    Answered by Naveen Sharma (Jan 13, 2017)
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0.025 moles of methane contain how much grams

Posted by SUNITHA D (Jan 12, 2017) (Question ID: 1324)

  • Answers:
  • Gram atomic mass of methane=CH4=12+4×1

    =16  no of moles=given mass÷gram atomic mass

    0:025=given mass÷16

    So,given mass=16×0:025

    Given mass=0:4 gram

    Answered by Ghanshyam Kumar (Jan 13, 2017)
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How far it is correct to say that both pressure and winds

conditions over india are unique. What Information would you use to support your answer?

Posted by s.saiarvind sridhar (Jan 12, 2017) (Question ID: 1318)

If 16 g of oxygen contains 1 mole of oxygen atoms, calculate the mass of one atom of oxygen. 

Posted by pratham srivastav (Jan 12, 2017) (Question ID: 1312)

  • Answers:
  • Ans.

    Molar mass of a substance is a mass of 6.023 X1023 molecules.

    Molar mass of Oxygen molecule i.e N is 2 X 8 = 16 g.

    Thus 6.023 X 1023 molecules weigh = 16 g

    1 molecule of Oxygen weighs = 16/6.02 X 1023 = 2.66 X 10-23 g

    Answered by Naveen Sharma (Jan 12, 2017)
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  • Ans. The mass of 1 atom = Gram atomic mass of atom/ 6.022 × 1023

    So, the mass of 1 atom of oxygen = Gram atomic mass of oxygen atom/ 6.022 × 1023 = 16g/ 6.022 × 1023 =

    2.66 × 10-23 g

    Answered by Payal Singh (Jan 12, 2017)
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If one mole of nitrogen molecules weighs 28 g, calculate the mass of one molecule of nitrogen in grams. 

Posted by pratham srivastav (Jan 12, 2017) (Question ID: 1311)

  • Answers:
  • Answer: The mass of 1 atom = Gram atomic mass of atom/ 6.022 × 1023

    So, the mass of 1 atom of nitrogen = Gram atomic mass of nitrogen atom/ 6.022 × 1023 = 28g/ 6.022 × 1023 =

    4.65 × 10-23 g

    Answered by Payal Singh (Jan 12, 2017)
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  • Ans. Molar mass of a substance is a mass of 6.023 X1023 molecules.

    Molar mass of nitrogen molecule i.e N is 2 X14 = 28 g.

    Thus 6.023 X 1023 molecules weigh = 28 g

    1 molecule of nitrogen weighs = 28/6.02 X 1023 = 4.65 X 10-23 g

    Answered by Naveen Sharma (Jan 12, 2017)
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In an experiment, 4.9g of copper oxide news obtained nfrom 3.92g  of copper . In another experiment,4.55g of copper oxide gave, on reduction, 3.64 g of copper . Show that these figure verify the law of constant proportion

Posted by Tanveer Singh (Jan 12, 2017) (Question ID: 1310)

  • Answers:
  • Case I

    Mass of copper= 3.92g

    Mass of copper oxide= 4.9g

    % of copper in oxide = (Mass of copper/Mass of copper oxide) x 100

    = 80%

    So, % of oxygen = 100-80= 20%


    Case II

    Mass of copper= 3.64g

    Mass of copper oxide= 4.55g

    % of copper in oxide = (Mass of copper/Mass of copper oxide) x 100

    = 80%

    % of oxygen= 100-80=20%

    Thus,copper oxide prepared by any of the given methods contains copper and oxygen in the same proportion by mass.Hence, it proves the law of constant proportions.

    Answered by Shweta Gulati (Jan 17, 2017)
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How to derive  speed = wavelength * frequency






Posted by Tanveer Singh (Jan 12, 2017) (Question ID: 1307)

  • Answers:
  • As we know, speed= Distance travelled/Time taken

    Suppose a wave travels a distance λ which is its wavelength in time T,

    λ / T

    Here T is the time taken by one wave. 1/T becomes the number of waves per second and is known as frequency of the wave.

    Thus v = λ x f

    i.e. Speed = Wavelength x Frequency

    Answered by Shweta Gulati (Jan 17, 2017)
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what is canal ray? 

Posted by Suresh Goyal (Jan 12, 2017) (Question ID: 1303)

  • Answers:
  • Canal rays: These are also known as anode rays which are made up of positively charged material particles known as protons. They are called as canal/anode rays because they seems to be coming from a perforated anode used in a discharge tube experiment. The charge to the mass ratio (e/m ratio ) is not constant for these rays, and has been found different for different gases used in the discharge tube. The mass of proton has been found to be nearly equal to that of hydrogen atom.(nearly 1).

    Answered by Naveen Sharma (Jan 12, 2017)
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  • An anode ray (also positive ray or canal ray) is a beam of positive ions that is created by certain types of gas discharge tubes. They were first observed in Crookes tubes during experiments by the German scientist Eugen Goldstein, in 1886.

    Answered by Payal Singh (Jan 12, 2017)
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  • positively rays

    Answered by Suresh Goyal (Jan 12, 2017)
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AOB is a right Triangle right angled at O=12.5 centimetre where C is the midpoint of AB that is AC =CB. AO =7 cm, find the area of triangle AOB.

Posted by Rohit Shaw (Jan 11, 2017) (Question ID: 1292)

Can water boil at 0 degree celcius? 

Posted by Kanha Dhameja (Jan 11, 2017) (Question ID: 1291)

  • Answers:
  • Yes you can! Only if By any means you make the vapour pressure of water at the 'desired' temperature (0°C if you like) equal to (or greater) the atmospheric pressure of that place, your water will boil. 
    Aliter, reduce atmospheric pressure. Keep the water in vacuum.

    Answered by Naveen Sharma (Jan 12, 2017)
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Explain the uses of sonar

Posted by SUNITHA D (Jan 10, 2017) (Question ID: 1266)

  • Answers:
  • SONAR is an apparatus which is used to find the depth of a sea or to locate the under-water things like shoals of fish,shipwrecks, and enemy submarines. It works by sending short bursts of ultrasonic sound from a ship down into sea-water and then picking up the echo produced by the reflection of ultrasonic sound from under-water objects. Thus, the time it takes for an echo to return is used to find out how far away something is. 

    Answered by Shweta Gulati (Jan 10, 2017)
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    • Sound navigation and ranging
    • It is used in detected sumarine , rocks , etc
    • It receives the depth of the sea
    Answered by Raman arora (Jan 10, 2017)
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1. What are the rules to be followed while entering the following in OOo Calc?

a) numbers

b) text

c) formulas

Posted by Ajaychandra Gupta (Jan 09, 2017) (Question ID: 1228)

Suggest  the calc functions that can be used for carrying  out following operations : calculate total  marks  of   a student if his marks in five subjects are  given in five different cells.

2. To calculate average sales made by salesman of a company , if sales made by each of the salesman is available.

3. To find  out the marks of top scorer in a class, if marks of all the  students are available. 

4.  To find  out minimum  quoted rate  from various quotations available.

Posted by Ajaychandra Gupta (Jan 09, 2017) (Question ID: 1226)

  • Yaar koi jaldi answer batao..... mujhe home work karni hai....

    Posted by Ajaychandra Gupta (Jan 09, 2017)
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