Question : If the radius of the base, and the height of a right circular cone are increased by 20%, what is the approximate percentage increase in volume?
Option 1: 60
Option 2: 68.8
Option 3: 72.8
Option 4: 75
Correct Answer: 72.8
Solution : Let the base radius and height of the cone be r and h respectively Then, volume = $\frac{1}{3}\pi r^2h=V$ If base radius is increased 20 %, new radius = $r\times \frac{120}{100}=\frac{6}{5}r$ Similarly, New height = $\frac{6}{5}h$ New volume = $\frac{1}{3}(\frac{6}{5}r)^2\times \frac{6}{5}h=\frac{216}{125} V$ Hence, percentage increase = $\frac{(\frac{216}{125}-1)V}{V}\times 100=72.8\%$ Hence, the correct answer is 72.8.
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Question : If the base radius and the height of a right circular cone are increased by 10%, then the percentage increase in the volume is:
Option 1: 30.2%
Option 2: 22.1%
Option 3: 33.1%
Option 4: 20.2%
Question : Which of the following statements is not correct?
Option 1: For a given radius and height, a right circular cone has a lesser volume than a right circular cylinder.
Option 2: If the side of a cube is increased by 10%, the volume will increase by 33.1%.
Option 3: If the radius of a sphere is increased by 20%, the surface area will increase by 40%.
Option 4: Cutting a sphere into 2 parts does not change the total volume.
Question : The height and the radius of the base of a right circular cone are in the ratio of 12 : 5. If its volume is 314 cm3, then what is the slant height of the cone? (Use $\pi$ = 3.14)
Option 1: 12 cm
Option 2: 11 cm
Option 3: 13 cm
Option 4: 14 cm
Question : A solid metallic sphere of radius 6.3 cm is melted and recast into a right circular cone of height 25.2 cm. What is the ratio of the diameter of the base to the height of the cone?
Option 1: 2 : 1
Option 2: 3 : 2
Option 3: 1 : 2
Option 4: 2 : 3
Question : The curved surface area of a right circular cone is $156 \pi$ and the radius of its base is 12 cm. What is the volume of the cone, in cm3?
Option 1: $192 \pi$
Option 2: $210 \pi$
Option 3: $240 \pi$
Option 4: $180\pi$
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