Question

The radius of a circle is increased by 1%. Find how much % does itsarea
increases?
A. 1.01%
B. 5.01%
C. 3.01%
D. 2.01%

Answer 1

d) 2.01% is the correct answer

since pi is unchanged in pi r sqaure, the value of r sqaure increases by 2.01% so the value of pi r sqaure also increase by 2.01%

Answer 2

answer : option (D) 2.01 %

explanation : Let the radius of circle is R

so, area of circle , A = πR²

radius of circle is increased by 1%

so, new radius of circle , R' = R + 1% of R = 1.01R

area of circle, A' = πR'²

= π(1.01R)² = 1.0201πR²

hence, percentage change in area of circle = change in area of circle/initial area of circle × 100

= (1.0201πR² - πR²)/πR² × 100

= (0.0201)πR²/πR² × 100

= 2.01 %

hence, option (D) is correct choice.