Question

The area of a circle is increased by 22 cm² when its radius is increased by 1 cm. The original radius of the circle is

• A. 3 cm
• B. 5 cm
• C. 7 cm
• D. 9 cm

Answer 1

Answer:

A. 3 cm

$\pi{(r + 1)^2}-\pi{r^2}= 22$

$\pi{(r^2+2r+1-r^2)}=22$

$2\pi{r}+\pi = 22$

$\frac{22}{7}{(2r+1)}=22$

2r + 1 = 7

2r = 6

r = 3 cm.