Question

The radius of a circle is increased by 40%. What is the percent increase in its area?

• A. 40%
• B. 96%
• C. 80%
• D. 160%

Answer 1

Answer:

B. 96%

Initial area = π × r2 New area = π × (1.4r)² = π × 1.96r² Percentage increase = [(1.96r² - r²) / r²] × 100 ⇒ Percentage increase = [(1.96 - 1) / 1] × 100 ⇒ Percentage increase = 0.96 × 100 ⇒ Percentage increase = 96%