Class 7 Maths Chapter 8 Comparing quantities Exercise 8.3 pdf notes:-

**Exercise 8.3** Class 7 maths Chapter 8 Pdf Notes:-

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## Ncert Solution for Class 7 Maths Chapter 8 Comparing quantities Exercise 8.3 Tips:

**Increase or Decrease as Per Cent**

There are times when we need to know the increase or decrease in a certain quantity as

percentage. For example, if the population of a state increased from 5,50,000 to

6,05,000. Then the increase in population can be understood better if we say, the

population increased by 10 %.

How do we convert the increase or decrease in a quantity as a percentage of the initial

amount? Consider the following example.

**PRICES RELATED TO AN ITEM OR BUYING AND SELLING**

The buying price of any item is known as its cost price. It is written in short as CP.

The price at which you sell is known as the selling price or in short SP.

What would you say is better, to you sell the item at a lower price, same price or higher

price than your buying price? You can decide whether the sale was profitable or not

depending on the CP and SP. If CP < SP then you made a profit = SP ā CP. If CP = SP then you are in a no profit no loss situation. If CP > SP then you have a loss = CP ā SP.

Let us try to interpret the statements related to prices of items.

ļ¬ A toy bought for ļ 72 is sold at ļ 80.

ļ¬ A T-shirt bought for ļ 120 is sold at ļ 100.

ļ¬ A cycle bought for ļ 800 is sold for ļ 940.

Let us consider the first statement.

The buying price (or CP) is ļ 72 and the selling price (or SP) is ļ 80. This means SP

is more than CP. Hence profit made = SP ā CP = ļ 80 ā ļ 72 = ļ 8

Now try interpreting the remaining statements in a similar way.

8.5.1 Profit or Loss as a Percentage

The profit or loss can be converted to a percentage. It is always calculated on the CP.

For the above examples, we can find the profit % or loss %.

Let us consider the example related to the toy. We have CP = ļ 72, SP = ļ 80,

Profit = ļ 8. To find the percentage of profit, Neha and Shekhar have used the

following methods.

**Try These** 1.A shopkeeper bought a chair for ļ 375 and sold it for ļ 400. Find the gain Percentage. 2.Cost of an item is ļ 50. It was sold with a profit of 12%. Find the selling price. 3.An article was sold for ļ 250 with a profit of 5%. What was its cost price? 4.An item was sold for ļ 540 at a loss of 5%. What was its cost price?

CHARGE GIVEN ON BORROWED MONEY OR SIMPLE**INTEREST**

Sohini said that they were going to buy a new scooter. Mohan asked her

whether they had the money to buy it. Sohini said her father was going

to take a loan from a bank. The money you borrow is known as sum

borrowed or principal.

This money would be used by the borrower for some time before it is

returned. For keeping this money for some time the borrower has to pay

some extra money to the bank. This is known as Interest.

You can find the amount you have to pay at the end of the year by adding the sum

borrowed and the interest. That is, Amount = Principal + Interest.

Interest is generally given in per cent for a period of one year. It is written as say 10%

per year or per annum or in short as 10% p.a. (per annum).

10% p.a. means on every ļ 100 borrowed, ļ 10 is the interest you have to pay for one

year. Let us take an example and see how this works.

**Interest for Multiple Years**

If the amount is borrowed for more than one year the interest is calculated for the period

the money is kept for. For example, if Anita returns the money at the end of two years and

the rate of interest is the same then she would have to pay twice the interest i.e., ļ 750 for

the first year and ļ 750 for the second. This way of calculating interest where principal is

not changed is known as simple interest. As the number of years increase the interest

also increases. For ļ 100 borrowed for 3 years at 18%, the interest to be paid at the end

of 3 years is 18 + 18 + 18 = 3 Ć 18 = ļ 54.

**Try These:-** 1.10,000 is invested at 5% interest rate p.a. Find the interest at the end of one

year. 2.3,500 is given at 7% p.a. rate of interest. Find the interest which will be received

at the end of two years. 3.6,050 is borrowed at 6.5% rate of interest p.a.. Find the interest and the amount

to be paid at the end of 3 years. 4.7,000 is borrowed at 3.5% rate of interest p.a. borrowed for 2 years. Find the

amount to be paid at the end of the second year.