Question : If the radius of a circle is increased by 50%, then what will be the percentage increase in the area of the circle?
Option 1: 225
Option 2: 125
Option 3: 150
Option 4: 175
Correct Answer: 125
Solution : Let the radius of the original circle = $r$ So, the area of the original circle = $\pi r^2$ Radius of circle after 50% increase = $r+\frac{50r}{100} =1.5r$ Area of new circle = $\pi \times 1.5^2 = 2.25r^2$ Percentage increase in area = $\frac{2.25\pi r^2- \pi r^2}{\pi ^2}\times 100$ = 125% Hence, the correct answer is 125.
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Question : If the radius of a circle is increased by 10%, what will be the percentage increase in the area of the circle?
Option 1: 19
Option 2: 20
Option 3: 21
Option 4: 23
Question : The radius of circle A is twice that of circle B and the radius of circle B is twice that of circle C. Their area will be in the ratio:
Option 1: 16 : 4 : 1
Option 2: 4 : 2 : 1
Option 3: 1 : 2 : 4
Option 4: 1 : 4 : 16
Question : If the height of the cylinder is increased by 35% and the radius is increased by 10%, what will be the percentage increase in the curved surface area of a cylinder?
Option 1: 46.5
Option 2: 45
Option 3: 48.5
Option 4: 49.7
Question : If the radius of a circle is increased by 16%, its area increases by
Option 1: 34.56%
Option 2: 32%
Option 3: 16%
Option 4: 17.28%
Question : If the radius of a sphere is doubled, then its surface area will be increased by:
Option 1: 100%
Option 2: 200%
Option 3: 300%
Option 4: 400%
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