Homework Help > CBSE Class 08
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If you multiply (xa) (xb)....... (xy) (xz) what is the answer?

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Solution : It ll be equal to Zero (0).
because xx = 0
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A does 20% less work than B. If A can finish a piece of work in 7 1/2 h then B can finish it in

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Ans. Let Time taken by B = x hours
then work done by B In 1 Hour = 1/x
as A does 20% less,
So work done By A in 1 Hour =(1/x) (20% *1/x)
=> 1/x  1/5x => 4/5x
Then time taken by A = 5x/4
according to Question, 5x/4 = 15/2
x = 6
So B can finish in 6 hours.
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According to question,
B can finish in 15/2 × 100 / (100 + 20)
= 25/4 = 6 1/4 h
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A alone can finish a piece of work in 10 days which B can do in 15 days.If they work together and finish it, then out of total wages of Rs 3000.A will get how much

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Wages are distributed according to the work done in a day.
as A takes = 10 days
one day work of A= 1/10
B Takes = 15 days
one day work of B= 1/15
Ratio: 1/10 : 1/15
3:2
Share of A = 3000×3/5 = 1800
Share of B = 3000×2/5 = 1200
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bring out the role of revolutionaries in the freedom movement in india

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 The Revolutionaries supplemented the national cause and carried the message of nationalism in the country and outside the country.
 They inspired the people to cast off the yoke of slavery and be prepared for any kind of sacrifice for the cause of freedom.
 They embraced death cheerfully arid were not scared of the physical and mental injuries inflicted upon them by the cruel rulers.
 Rass Behari Bose, Chander Shekhar Azad, Lala Hardyal M.A., Madan Lal Dhingra and . S. Ajit Singh succeeded in expanding the movement of freedom to other countries as well.
 Sardar Bhagat Singh and his companions faced brutalities of Britishers boldly, cheerfully and willingly for the cause of their motherland—India.
 They gave the nationalist movement a new turn.
 Netaji Subhash Chandra Bose organized Azad Hind Fauj and gave us the slogan ‘Give me blood, I will give you freedom.
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Describe the threat to the beauty of Taj Mahal ?

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Acid rain is a major threat to the beauty of the Taj Mahal. When acid rains fall on themonument (that is completely made of marble), they react with marble to form a powderlike substance that is then washed away by the rain. This phenomenon is known as marble cancer. Also, the soot particles emitted from the Mathura oil refinery located near Agra is leading to the yellowing of the marble.
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Taj Mahal is made up of white marble. Marble is composed of calcium carbonate. Calcium carbonate reacts with acids and thus gets corroded. This is the reason; acid rain is damaging the Taj Mahal. This wonderful monument does not look white but is looking pale and dull. If corrective measures are not taken, the future generations may not be able to see the beauty of the Taj.
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2 men or 3 women can do a piece of work in 16 days . In how many days can 4 men and 6 women do the same work .

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2 Men = 3 Women
1 Man = 3/2 Women
4 Man + 6 Women = 4*3/2 + 6 = 12 Women
3 Women can do Work in = 16 days
1 Woman can do work in = 16*3 = 48 days
12 Women can do Work in = 48/12 = 4 days
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(1/2 + 1/3) can do work = 1/16
1 can do work = 1/16 × 6/5
(1/4 + 1/6) can do work = 1/16 × 6/5 × 5/12 = 1/32
Therefore 4 men and 6 women can do the work in 32 days.
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4 days us the correct answer.
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32
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What is the formula of area of triangle?

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Area of Triangle = B*H/2
Where B Base of Triangle
And H is height of Triangle
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1/2*base*height
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How many vertices are there for a cone ?

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A cone has 1 vertex as vertex is a point where 2 lines meet and cone is curved from bottom but has a vertex at top
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Ans. None. A cone does not have a vertex. A vertex is defined as a point where two lines meet; a triangle has three vertices.
However, a cone is a threedimensional figure and has a curved surface.
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LMNO IS A RECTANGLE , ABCD IS A SQUARE SUCH THAT AM =11 cm and OD = 14cm find area of rectangle

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define water polluntant

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Water pollution is an appalling problem, powerful enough to lead the world on a path of destruction. Water is an easy solvent, enabling most pollutants to dissolve in it easily and contaminate it. The most basic effect of water pollution is directly suffered by the organisms and vegetation that survive in water, including amphibians. On a human level, several people die each day due to consumption of polluted and infected water.
Water pollutant:
 Industrial waste
 Sewage and waste water
 Mining activities
 Marine dumping
 Accidental Oil leakage:
 Burning of fossil fuels
 Chemical fertilizers and pesticides
 Leakage from sewer lines
 Radioactive waste
 Animal waste
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what are the diferent ways in which water gets contaminated

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Though water pollution may occur from a variety of sources, there are two terms used to describe how the water became polluted.
When water is polluted from point sources, this is pollution from a discrete location. This discrete location could be a factory, a sewer pipe or a runoff from a single farm. The BP oil spill in 2010 is an example of point source pollution, because the massive amount of oil leaked from a single point of origin.
Water pollution may also be from nonpoint source pollution, which is when several points of contamination over a large area contribute to the pollution of a water body. For example, one water body may be contaminated by multiple sources like agricultural runoff, city street runoff, construction sites and residential lawns. The Mississippi River is at great risk for nonpoint source pollution because it is so large and is exposed to a variety of possible pollution sources.
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What is fertilization in human?

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Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the fallopian tube. The result of this union is the production of a zygote cell, or fertilized egg, initiating prenatal development.
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The length and breadth of a rectangle are in the ratio 4:3. If the diagonal measures 25 centimeter then find the perimeter.

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Let the length and breadth of the rectangle be 4x and 3x cms.
Diagonal= 25 cm
Applying pythagoras theorem,
25^{2}= (4x)^{2}+(3x)^{2}
16x^{2}+9x^{2}=625
25x^{2}=625
x^{2}=25
So, x=5
Length= 4x=4 x 5= 20cm and breadth = 3x= 3 x 5 =15cm
Perimeter of rectangle= 2(l+b) =2(20+15)=2(35)= 70cm
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what is the shape of our galxy the milkey way

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The shape of our galaxy milky way is barred spiral galaxy in which the central elliptical buldge of closely packed starts lying in the direction of Sagittarius.
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wo are orientalist?

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Orientalist is a person who studies the languages and cultures of East and Southeast Asia.
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activity to prove the identity ^{(}^{a}^{2b2)=a2+b22ab}

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$Objective:\phantom{\rule{0ex}{0ex}}$
$Toverifytheidentity{\left(a+b\right)}^{2}={a}^{2}+{b}^{2}+2abbypapercuttingandpasting$
$Formulaused:\phantom{\rule{0ex}{0ex}}$
$Areaofsquare=side\times side\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}$
$areaofrec\mathrm{tan}gle=length\times breadth$
$Materialsrequired:\phantom{\rule{0ex}{0ex}}$
$Asheetofwhitepaper,sheetsofglazedpaper(differentcolours),apairofscissors,gluestickandageometrybox$
$Procedure:\phantom{\rule{0ex}{0ex}}$
$Takedistinctvaluesofaandb,leta=4units;b=2units.$
$1.Cutasquareofsidea=4unitonaglazedpaper\left(purple\right).$
$2.Cutasquareofsidebonaglazedpaper\left(blue\right)$
$3.Now,Cut2rec\mathrm{tan}glesoflengthaandbreadthbfromthirdglazedpaper\left(red\right).$
$4.DrawasquarePQRSof(a+b)=(4+2)=6unitsonawhitepapersheet$
$5.PasethesquareIandIIand2rec\mathrm{tan}glesIIIandIVonthesamewhitesquaredpaper.$
$ArrangeallthepiecesonthewhitesquaresheetinsuchawaythattheyfromasquareABCD$
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2x^{2}+11x+12

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2x^{2}+11x+12 is a quadratic polynomial that is , ax^{2}+bx+c where a=2 ,b=11 ,c=12
Multiply a to b i.e., 2*12=24 now factorise 24= 2*2*2*3
Now arrange these terms in such condition so that we could get the middle term of quadratic polynomial.
Therefor, 2*2*2 * 3   8 + 3 =11
So, 2x^{2 }+8x+3x +12
Now take common
2x(x +4) +3 (x+4)
(X+4)(2x+3)

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Find the altitude of a trapezium the sum the lengths of whose bases is 6.5 cm and whose area is 26 cm

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As per the formula of trapezium,
1/2(l_{1+}l_{2}) *h
So, sum of parallel sides 6.5cm
Area= 26cm^{2}.
Therefor,
26 =1/2(6.5)*h
h =26*2/6.5
h =52/6.5
h =8cm

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sheila is now 15 yers older than hey younger brother sanjay. ten years from now, sheila will be twice as old as sanjay. find the present age of each of them?

Let the present age of shiela = x let the present age of Sanjay = y
According to question, shiela is now 15 years older than her younger brother Sanjay.
Therefor, x= 15+y (1) Ten years from now ,shiela will be twice as old as Sanjay. So, x+10= 2(y+10)
X+10=2y+20 _______________(2)
Put the value of x in equation (2).
Therefor, 15+y+10 2y+20
25+y =2y+20
2520= 2yy
5=y so, age of Sanjay =5 years
Put the value of y in equation(1)
Therefor, x= 15+5
X=20
So, age of shiela =20 years.
Let the present age of shiela = x let the present age of Sanjay = y
According to question, shiela is now 15 years older than her younger brother Sanjay.
Therefor, x= 15+y (1) Ten years from now ,shiela will be twice as old as Sanjay. So, x+10= 2(y+10)
X+10=2y+20 _______________(2)
Put the value of x in equation (2).
Therefor, 15+y+10 2y+20
25+y =2y+20
2520= 2yy
5=y so, age of Sanjay =5 years
Put the value of y in equation(1)
Therefor, x= 15+5
X=20
So, age of shiela =20 years.
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A point within an equilateral triangle whose perimeter is 30 m is 2m from one side and 3 m from another side. Find its distance from third side?

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Find : 4yz(z²+6z16)+2y(z+8)

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4yz(z^{2}+6z16)+2y(z+8)
= 4yz^{3}+24yz^{2}64yz+2yz+16y
= 4yz^{3}+24yz^{2}62yz+16y
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Q1 Is 326010 divisible by 3 or not?
Q2 If 70% of X is 35 kg, find the value of X?
Q3 If the base of the triangle is doubled, height is halved then its area will be?
SECTION B
Q4 A school hostel has enough food for 800 students for 80 days. How long the food lasts if 50 more
students join the hostel?
Q5 The area of trapezium is 34 sq. cm and length of one of the parallel sides is 10cm. And its height is
4cm. Find the length of the other side?
Q6 Mohini spends 30% of the salary on House Rent, 25% on Education of her children and 40% on food
items. Find her salary if she saves Rs. 1470 per month.
Q7 Find the compound interest on Rs. 8000 for 1 year at 10% per annum payable yearly

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how are cells classified

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Mainly there are two types of cells which are Eukaryotic and Prokaryotic.
The Prokaryotic cells do not have a well defined nuclear membrane. Eg blue green algae and bacteria.
The Eukaryotic cells have a well defined nuclear membrane. Example human beings.
On the basis of shape we have round cells, elongated cells and branched cells.
For example nerve cell is the longest and branched cell in a human body so that it can transmit the messages rapidly.
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Cells are classified into two categories,
1) prokaryotic cells
2)Eukaryotic cells
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what is eutrophication?
what is hydrophobic?

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Eutrophication is enrichment of ecosystem with chemical nutrients mostly by compounds of Nitrogen and Phosphorus is called Eutrophication.It results in growth of algae in water and deteriorates the water quality.
Hydrophobic hydro+phobic
Hydro means water and phobic means hating or repelling
So it is the property of molecule which is water repelling in nature.They are non polar in nature and do not mix with water.for example oil,greese etc
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What is the value of pie

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Pie is a mathematical constant , the ratio of circle's circumference to its diameter approximated as 3.14159. Also the value of π= 22/7
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who wrote national athem for india

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National anthem of India was written by Rabindranath Tagore.
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Rabindranath Tagore wrote national anthem for india. It was first sung on 27 December 1911 at the kolkata session of Indian national congress.
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4^{x } 4^{x1 } = 24 find the value of x ?

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4^x 4^x1 = 24
4^x(11/4)= 24
4^x =24* 4/3 = 32 = 4^ (2+1/2)
x=2.5 or 5/2
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Take 4^{x1} common we get:
4^{x1}(41) = 24
$\Rightarrow {4}^{x1}=8\phantom{\rule{0ex}{0ex}}\Rightarrow {2}^{2(x1)}={2}^{3}\phantom{\rule{0ex}{0ex}}\Rightarrow 2x2=3\phantom{\rule{0ex}{0ex}}\Rightarrow x=\frac{5}{2}$
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 When you fly in an aeroplane we say that every door or window should be closed as there is very less oxygen but when we fly in a helicopter we are opening the doors. Can you find the reason for it? How do we get oxygen to breath when we fly in a helicopter?

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Aeroplane flys at much higher altitude than the helicopter. Therefore the decrese in air pressure in case of aeroplne is much more than helicopter at which they fly. Now we all know that inside the aeroplane we need to maintain the atmospheric pressure to keep all our biological systems properly. so an equillibrium of pressure is maintained there. if the doors and windows are opened that equillibrium will be disturbed and hence the situation can be fatal.
Since Helicopter can rise only upto a certain level where the air density is lower but not fatal for us so no air pressure equillibrium is maintained. Therefore the doors and windows can be open
Moreover drag caused by the air is much more in case of aeroplane than helicopter because the former runs in much faster speed than latter. This drag also hamper the functioning of the system of an aeroplane. so the windows are closed. Since the drag in case of helicopter is not much so it doesnot affect the working of a helicopter.
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