Question

The ratio between the diameters of two circles is $3:5,$ then find the ratio between their areas.

• A. $9:25$
• B. $19:25$
• C. $29:25$
• D. $39:25$

Answer 1

Answer: (A)

$9:25$

Diameter = 2 $\times$ radius.

Thus, ratio of diameter = ratio of radius

$\therefore$ ratio of radius $=3:5$

Area of a circle $=\pi r^2$

$\therefore$ ratio of the area $={r_1}^2:{r_2}^2$

$=3^2:5^2$

$=9:25$