Let the CP of first fan be Rs a
CP of second fan = Rs (3120 - a)

Profit on first fan = 36%
SP of first fan = a + 36% of a
= a + 36a / 100
= 136a/100

Loss on second fan = 5%
SP of second fan = (3120 -a) - 5% of (3120-a)
= (3120 -a) - [5(3120 - a) / 100]

According to question
SP of first fan = SP of second fan
136a / 100 = {(312000-100a) - (15600 - 5a)} / 100
=> 136a = 312000 - 100a - 15600 - 5a
=> 241a = 296400
=> a = 1300 approx

CP of first fan = Rs 1300
Cp of second fan = Rs 1820

The presence of hydrogen and helium in very high amount leads the sun to be the only source of heat and light for all planets as hydrogen and helium being a light element do nuclear fusion to form enormous energy with production of heat and light.

The major products (or fractions) of petroleum refining are:

• Petroleum gas
• Diesel
• Petrol
• Kerosene
• Lubricating oil
• Paraffin wax
• Bitumen

  -2(6 + 7)

= - 2(13)

= - 26

• A Hub is a networking device that allows you to connect multiple PCs to a single network, whereas a Switch connects various devices together on a single computer network.
• A Hub operates on the physical layer, whereas Switch operates on the data link layer.
• Hub uses Half-duplex cable on the other hand Switch uses Full duplex cables
• Hub is a passive device while the switch is an active device
• Hub uses electrical signal orbits while switch uses frame & packet
• Hub and switch are both used in LAN

There are 14 punctuation marks that are commonly used in English grammar. They are the period, question mark, exclamation point, comma, semicolon, colon, dash, hyphen, parentheses, brackets, braces, apostrophe, quotation marks, and ellipsis

Click on the given link:

<a href="https://i.gov.ph/wp-content/uploads/2015/06/punctuation.pdf" ping="/url?sa=t&source=web&rct=j&url=https://i.gov.ph/wp-content/uploads/2015/06/punctuation.pdf&ved=2ahUKEwjDnsyHlaztAhXkzzgGHeBCAtgQFjABegQIAhAC&cshid=1606804519086963" rel="noopener" target="_blank">Notes on Punctuation</a>

The kaleidoscope is an instrument or a toy containing inclined plane mirrors which produce multiple reflections of coloured glass pieces and create beautiful patterns. The coloured glass pieces act as objects and the inclined plane mirrors form multiple images of these glass pieces by repeated reflections, which look like beautiful patterns or designs.

To make a kaleidoscope, take three rectangular mirror strips about 15 cm long and 4 cm wide each and join them together to form a prism. Fix them in a circular cardboard tube or tube of a thick chart paper. Close one end of the tube by a cardboard disc having a hole in the centre, through which you can see. To make the disc durable, paste a piece of transparent plastic sheet under the cardboard disc. At the other end, touching the mirrors, fix a circular plane glass plate. Place on this glass plate several small pieces of coloured glass. Close this end of the tube by a ground glass plate. Allow enough space for the colour pieces to move around.

To make a kaleidoscope, get three rectangular mirror strips each about 15 cm long and 4 cm wide. Join them together to form a prism as shown in Fig. (a). Fix this arrangement of mirrors in a circular cardboard tube or tube of a thick chart paper. Make sure that the tube is slightly longer than the mirror strips. Close one end of the tube by a cardboard disc having a hole in the centre, through which you can see [Fig (b)]. To make the disc durable, paste a piece of the transparent plastic sheet under the cardboard disc. At the other end, touching the mirrors, fix a circular plane glass plate [Fig (c)]. Place on this glass plate several small pieces of coloured glass (broken pieces of coloured bangles). Close this end of the tube by a ground glass plate. Allow enough space for the colour pieces to move around.

improper

Jody was a small, brave and sensitive boy. He was with his father when he (his father) was bitten by a rattlesnake. His father quickly killed a doe and used its heart and liver to draw out the snake’s poison. Jody was happy to see that his father got a new life but at the same time he was worried for the little fawn who was left alone without its mother. He wanted to bring back the fawn. He requested his father to allow him to go to the forest to find the fawn. He told him that he didn’t need to drink milk because he was now a big boy. He would give the milk to the fawn. He also said that it was ungrateful to leave the fawn to starve. His father was in a fix. He couldn’t say “no’ to his son. And finally allowed him (Jody) to go to the forest to find the

Let the current age of Rahul and Haroon be 5x and 7x respectively

Four years later their ages become 5x + 4 and 7x + 4 respectively.

According to the question,

5x + 4 +7x + 4 = 56

or 12x + 8 = 56

Transposing 8 to the RHS we get,

12x = 48

Dividing both sides by 12 gives,

x = 48/12 = 4

Thus current age of Rahul = 5×4 = 20

Haroon = 7×4 = 28

1. Rods and Cones are the photoreceptors found in the eye, rods have rod-like structure and provide twilight vision, while cones are of the cone shape, fewer in number and provides the vision in the day or bright light.
2. Rods are found around the boundary of the retina, whereas cones are there in the centre of the retina.
3. Out of the 125 million photoreceptors, rods are about 120 million in the human eye and cones are 5 million photoreceptors.
4. The outer segment is cylindrical of rods which contain rhodopsin pigment, made up of Vitamin A, while the outer segment is conical of cones which contain iodopsin pigment.
5. Cones provide colour vision, which is of three types: red, blue and gree, whereas rods cells do not give colour vision, they do not have any differentiation.
6. Lack of the rhodopsin in the rods may cause night blindness, while lack of the iodopsin in the cones may cause colour blindness.
7. Rods provide the vision in the dull light (darkness or night), whereas cones are known to give the vision during the day or bright light.

1. Why did Tilly’s family come to Thailand?
2. What were the warning signs that both Tilly and her mother saw?
3. Do you think Tilly’s mother was alarmed by them?
4. Where had Tilly seen the sea behaving in the same strange fashion?
5. Where did the Smith family and the others on the beach go to escape; from the tsunami?
6. How do you think her geography teacher felt when he heard about what Tilly had done in Phuket?

Answer: 

1. Tilly’s family had come to Thailand to celebrate Christmas.
2. Both saw the sea rise and it started to foam and form whirlpools.
3. No, Tilly’s mother was not alarmed by them.
4. Tilly had seen the strange sea behaviour in a video.
5. They went to the third floor of the hotel and were saved.
6. She felt very pleased and satisfied.

Rewrite 9p²

9p² as (3p)²

Now,

(3p)²−16

Rewrite 16 as 4²

(3p)² − 4²

Since both terms are perfect squares, factor using the difference of squares formula, a2−b2=(a+b)(a−b) where a=3p and b=4

(3p+4)(3p−4)

When a photo-diode is reverse biased, the width of depletion layer increases as compared to forward biased and a small reverse current (dark current) flows through the diode . Now , when the light is incident on the junction, electron-hole pairs are generated in depletion layer in a big amount (due to broad depletion layer) and these charge carriers can easily cross the barrier, hence contribute to current across the diod.

We can say that in reverse bias, diode changes the incident light to current , more effectively due to broad depletion layer i.e. when the diode is reversed biased , no ordinary current flows and the detection of the photo current is much easier.

The process in which a volatile liquid is first vaporised at its boiling point and the vapours are condensed to get back the liquid in pure form is called distillation.

If the difference in boiling points of the liquids in the mixture is less than 250C the method of fractional distillation is used to separate them. 

Fractional distillation method is same as simple distillation except that in the apparatus a fractionating column is fitted in between the distillation flask and the condenser.

It makes the appratus more efficient . A fractionating column is a wide tube packed with glass beads, which provides a larger surface area of cooling. Vapours of liquid having higher boiling point get condensed on the surface of these beads, while the vapours of lower boiling point liquid pass on upwards. Length of the column also increases the efficiency of the process.

Example:  In an oil refinery, the different fraction of petroleum products are separated by fractional distillation of crude petroleum. 

Burning of coal in absence of air to obtain some useful constituents is called destructive Distillation. Following constituents are obtained from this process :

(i) Coke : It is a hard porous substance which is almost the purest form of carbon. It is used in manufacture of steel and in extraction of many metals.

(ii) Coal-tar : It is a black liquid with unpleasant smell. It is a mixture of about two hundred substanes which are very useful in our day to day life. They are used in drugs, plastics, paints, photographic materials, synthetic dyes, roofing materials, perfumes, explosives etc. Insect repellants like naphthalene is also obtained from it. Earlier, it was also used for surfacing of roads.

(iii) Coal gas : This gas is also obtained during destructive distillation of coal. It is used as fuel in coal processing plants and in various other industrial units situated near coal processing plants. Coal gas was used by the Americans and the Britishers for street lighting.