Page 88 - Maths Skills - 7

86 Maths

8. If a tap can fill a 1 litre container in 10 s, how much time will it take to fill a container of capacity
2.5 litre?
9. 50 kg of rice costs ` 1,650. Find the quantity of rice that can be purchased in ` 4,125.

10. A train travels 295 km in 5 hrs. How many kilometres will it cover in 8 hrs 15 minutes?

PERCENTAGE
In our day-to-day life, we often come across many situations where we use the word 'per cent' such as

(i) Siddhie secured 95% in maths. (ii) 40% off season discount
(iii) Rate of interest of a particular bank is 7% (iv) 70% of air consists of Nitrogen.
In all these statements we have used the symbol (%) for the per cent. The term ‘per cent’ is derived from the latin
word ‘Percentum’ which means per hundred or out of hundred. Per cent is used for comparison. For example,
Pinky got 120 marks out of 200 in maths and her brother got 175 out of 250. They are not able to decide who
has performed better by just looking at the marks. To compare their marks, we convert their marks to equivalent
fractions with denominator as 100, i.e. percentage.
Pinky's % 120 = 120 × 100% = 60% Absorbing Facts
200 200 1

Brother's % 175 = 175 × 100% = 70% % = 100
250 250

Now we conclude that her brother has performed better.
Let’s learn to convert fractions into percentage and vice versa.

(i) Conversion of a Fraction into Percentage
In order to convert a fraction into per cent, multiply the fraction by 100 and put the ‘%’ sign.

3 3
For example, to convert into per cent. i.e., × 100% = 75%
4 4
6 6
Similarly, in per cent = × 100 (%) = 120%.
5 5

Let’s Attempt

Example 1: Convert each of the following into percentage:

3 7 19 3
(i) 2 (ii) (iii) (iv) 5
5 50 32 10

3 13 7
Solution: (i) 2 = × 100% = 260% (ii) × 100% = 14%
5 5 50
19 3 53
(iii) × 100% = 59.375% (iv) 5 = × 100% = 530%
32 10 10
4
Note: Do you know we have one more method of finding the percentage by changing into a fraction with
5
denominator as 100?

4 = 420× = 80 = 80%
5 520× 100