What’s the radius, volume of these cylinders?
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 cylinder is decreased by 50% and the height is increased by 50% to form a new cylinder, the volume will be decreased by?
a) 75% b) 62.5% c) 25% d) 0%
Ans: b
Solution: 50% = -50/100
= -1/2, 50% = 50/100 = 1/2
volume = 兀r²h
radius —> 2 : 1
r² —> 4 : 1
height —> 2 : 3
8 : 3
-5/8 × 100% = – 62.5%
2. Each of the radius of the base and the height of a right circular cylinder is increased by 10%. The volume of the cylinder is increased by?
a) 19.5% b) 3.31% c) 14.5% d) 33.1%
Ans: d
Solution: 10% = 10/100
= 1/10, 10% = 10/100 = 1/10
volume = 兀r²h
radius —> 10 : 11
r² —> 100 : 121
height —> 10 : 11
volume —> 1000 : 1331
331/1000 × 100% = 33.1%
3. If the radius of a cylinder is increased by 120% and its height is decreased by 40%, what is the percentage increase in its volume?
a) 190% b) 190.4% c) 211% d) 211.4%
Ans: b
Solution: 120%
= 120/100 = 6/10,
40% = -40/100 = -2/5
volume = 兀r²h
radius —> 5 : 1
r² —> 25 : 121
height —> 4 : 3
volume —> 125 : 363
238/125 × 100% = 190.4%
4. If the radius of the cylinder is decreased by 20%, then by how much percent must the height be increased so that the volume of the cylinder remains same?
a) 50.25% b) 56.25% c) 60.25% d) 66.25%
Ans: b
Solution: 20% =
-20/100
= -1/5
Volume
= 兀r²h
radius —> 5 : 4
r² —> 25 : 16
height —> 16 : 25 (volume remains same)
9/16 × 100% = 56.25%
5. Volume of a cylinder is increased by 43% when its height is decreased by 15 5/13%, then find the percentage change in curved surface area of a cylinder?
a) 10% b) 11%
c) 12% d) 13%
Ans: a
Solution: 43% = 43/100,
15 5/3% = -2/13
Volume = 兀r²h
V/h = r²
V —> 100 : 143
h —> 13 : 11
r² —> 100 × 11 : 13 × 143
r —> 10 : 13
CSA —> 10 × 13 : 13 × 11
10 : 11
1/10 × 100% = 10%
M Venkat
Director
MVK Publications
Dilsukhnagar
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