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4 250
Solution: (a) 4% of 250 = × 250 = = 10
100 25 Think and Answer
.
85 85 391 1 During rainy season 18%
(b) 8.5% of 920 = × 920 = × 920 = = 78 students of Minki’s class, which
100 1000 5 5 has 50 students were absent in
18 324 a month. How many students
(c) 18% of 180 kg = × 180 kg = kg
100 10 were absent?
= 32.4 kg or 32 kg 400 g

15 15
(d) 15% of 1 hour = × 1 hr = × 60 min = 9 min
100 100

Example 10: In an examination, Nisha scored 88% marks. If the total marks in the examination
were 800, what were the marks obtained by her?
Solution: We have, the total marks in the examination = 800

Since, Nisha scored 88% marks out of the total marks.
88
Therefore, 88% of 800 = × 800 = 704
100
Thus, she obtained 704 marks in the examination.
Nakul: Conversely, we can also find the whole quantity or number whose percentage of a part is given.

Suppose your friend Minki spent 70% of her pocket money which is `210. Can you tell the amount
of pocket money she get in the whole month?
In such situation, we consider the whole quantity as number x and find the value.
Let the total pocket money she gets in the month be `x.

Since, she spent 70% of her pocket money, which is `210.
Therefore, 70% of x = `210 Quick Check

70 1. 14 is 20% of what number?
× x = `210 2. If 28% of a certain quantity of
100 grain is 140 kg, find the whole
×
x = ` 210 100 quantity of the grain.
70
x = `300

Thus, Minki got `300 as a pocket money in the whole month.
Example 11: Find the number/quantity whose:
(a) 20% is `450 (b) 12% is 42 litre

Solution: (a) Let 20% of x is `450. (b) Let 12% of x is 42 litre.
20 12
× x = `450 × x = 42 litre
100 100
1 3
5 × x = `450 25 × x = 42 litre
×
x = `(450 × 5) x = 42 25 litre
x = `2250 3
x = 14 × 25 litre = 350 litre
Thus, 20% of `2250 is `450. Thus, 12% of 350 litre is 42 litre.

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