Page 88 - ICSE Math 8

3. Simmi’s income is 30% more than Ricky’s income. Find by how much percentage is Ricky’s income less
than that of Simmi’s?
4. Puneet is 20% younger than Raj. By what per cent is Raj elder than Puneet?
5. The price of rice is increased by 25% in the month of January. By what per cent should it be reduced in
February to bring it back to its original price?
6. The monthly salary of Divesh has increased from ` 15,000 to ` 16,500. Find the percentage increase in
his salary.
7. A number when increased by 20% becomes 72. What will it become if it is decreased by 10%?

8. Last month, the price of oranges was ` 60 per dozen. This month they are being sold at ` 60 per 8 oranges.
Find the percentage increase in the price of oranges.

AT A GLANCE

¾ Per cent means ‘out of hundred’ or ‘for every hundred’. It is denoted by the symbol ‘%’.
¾ To convert a fraction or a decimal into percentage, multiply it by 100 and put the symbol of percentage.
¾ To convert percentage into a fraction or a decimal, remove the symbol of percentage and divide it by 100.
¾ To express one quantity as a percentage of the other, divide the first quantity by the second and then
multiply by 100%.
¾ To find the percentage of a given quantity, express the given per cent as a fraction of 100 and multiply
by the given number.
¾ To find the number from a given percentage of the number, write the given percentage as a fraction of
100 and then divide the given number by this fraction.
Increase in value
¾ Increase in percentage = Original value × 100%

Decrease in value
¾ Decrease in percentage = Original value × 100%

¾ If any given number is increased or decreased by x%, then new number =   100 x±   × original number.
 100 

MENTAL MATHS

1. Write True or False.
(a) 32% of 250 is 80.
(b) If 400 decreases to 350, then the decrease in percentage is 15%.
(c) If 30 increases by 42%, then the new number is 42.6.

(d) 75% of 50 = 30% of 125
2. Fill in the blanks.
(a) 22% of ________ is 286.
(b) In an examination, if 75% students out of 3,224 scored A grade, then the number of students who
did not score A grade is ________.
(c) If the price of petrol increases from ` 52 per litre to ` 54 per litre, the increase in percentage is
________.
(d) 12.5% of 650 is ________.

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