Class 7 Maths Chapter 8 Comparing quantities Exercise 8.3 pdf notes:-
Exercise 8.3 Class 7 maths Chapter 8 Pdf Notes:-
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 – CP. If CP = SP then you are in a no profit no loss situation. If CP > SP then you have a loss = CP – SP.
Let us try to interpret the statements related to prices of items.
A toy bought for 72 is sold at 80.
A T-shirt bought for 120 is sold at 100.
A cycle bought for 800 is sold for 940.
Let us consider the first statement.
The buying price (or CP) is 72 and the selling price (or SP) is 80. This means SP
is more than CP. Hence profit made = SP – CP = 80 – 72 = 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 = 72, SP = 80,
Profit = 8. To find the percentage of profit, Neha and Shekhar have used the
Try These 1.A shopkeeper bought a chair for 375 and sold it for 400. Find the gain Percentage. 2.Cost of an item is 50. It was sold with a profit of 12%. Find the selling price. 3.An article was sold for 250 with a profit of 5%. What was its cost price? 4.An item was sold for 540 at a loss of 5%. What was its cost price?
CHARGE GIVEN ON BORROWED MONEY OR SIMPLE
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 100 borrowed, 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., 750 for
the first year and 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 100 borrowed for 3 years at 18%, the interest to be paid at the end
of 3 years is 18 + 18 + 18 = 3 × 18 = 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.