Paper 1 · Mathematical Reasoning and Aptitude
UGC NET June 2023 (20.06.2023) Shift-I
If the radius of a circle is increased by 10 percent, its area will increase by
A10%
B100%
C20%
D21% ✓ Correct
Correct answer: (D) 21% — The area increases by 21 percent, so the answer is 21 percent.
Explanation
★The area increases by 21 percent, so the answer is 21 percent.
★The area of a circle is proportional to the square of its radius.
★A 10 percent increase multiplies the radius by 1.1.
★So the new area is 1.1 squared times the old area.
★That is 1.21 times the old area.
★The increase is 0.21 of the old area.
★As a percentage this is 21 percent.
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