Sample questions to calculate percentage

This article is in continuation to the last article focusing on the percentage topic. Here are some practice questions along with solutions that will help you in your preparation for the State government recruitment jobs.

1. If the radius of a circle is decreased by 20%, its area is decreased by?

a) 20% b) 40%
c) 36% d) 15%

Ans: c

Solution: 20% = -20/100
= -1/5
Area = 兀r2
Radius —> 5 : 4
Area —> 25 : 16

-9/25 × 100% = – 36%

 

2. If each edge of a cube is increased by 40%, then the percentage increase in its surface
area is?

a) 40% b) 60% c) 80% d) 96%

Ans: d

Solution: 40% = 40/100
= 2/5
Surface area = 6a²
Edge —> 5 : 7
Surface area —>
25 : 49
24/25 × 100%
= 96%

 

3. The percentage increase in the surface area of a cube when each side is doubled is?

a) 50% b) 150%
c) 200% d) 300%

Ans: d

Solution: 100% = + 100/100 = + 1
Surface area = 6a²
Edge —> 1 : 2
Surface area —>
1 : 4

3/1 × 100% = 300%

 

4. If each side of a cube is decreased by 20%, then the percentage decrease in its surface area is?

a) 20% b) 25% c) 35% d) 36%

Ans: d

Solution: 20%
= -200/100 = -1/5
Surface area = 6a²
Side —> 5 : 4
Surface area —> 25 : 16

-9/25 × 100%
= -36%

 

5. If each side of a cube is increased by 10%, then the percentage increase in its volume is?

a) 33.1% b) 33.5%
c) 30% d) 32.5%

Ans: a

Solution: 10% = + 10/100
= + 1/10
Volume = (Side)³
Side —> 10 : 11
Volume —> 10³ : 11³
1000 : 1331
331/1000 × 100%
= 33.1%
 

M Venkat
Director
MVK Publications
Dilsukhnagar
7671002120