If the radius of a circle is decreased by 30%, the area decreases by: MCQ with Answer and Explanation

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If the radius of a circle is decreased by 30%, the area decreases by:

A. 51%

B. 49%

C. 60%

D. 42%

Answer: Option A

Solution (By JKSSB Mock Tests)

New area = 0.7² = 0.49, decrease 51%.

This question belongs to: Maths Percentage

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Question #1

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A man covers a distance at a speed of 60 kmph and returns back at a speed of 40 kmph. What is his average speed for the whole journey?

A. 55 kmph

B. 48 kmph

C. 50 kmph

D. 52 kmph

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Correct Answer: Option B

Explanation:
Average speed = 2×60×40/(60+40) = 4800/100 = 48 kmph. (Note: Not percentage but included as tough TSD).

This question belongs to: Maths Percentage

Question #2

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What is 33.33% of 99?

A. 66

B. 33

C. 11

D. 99

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Correct Answer: Option B

Explanation:
33.33% is equivalent to the fraction 1/3. (1/3) * 99 = 33.

This question belongs to: Maths Percentage

Question #3

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Find the single equivalent discount for successive discounts of 10% and 20%.

A. 25%

B. 28%

C. 30%

D. 32%

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Correct Answer: Option B

Explanation:
Equivalent discount = a + b - (ab / 100). 10 + 20 - (10 * 20 / 100) = 30 - 2 = 28%.

This question belongs to: Maths Percentage

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