Question

If the radius of a sphere is increased by 2 cm, then its surface area increases by 704 cm². Using π = 22/7, find the radius of the sphere before the increase

• A. 14 cm
• B. 15 cm
• C. 16 cm
• D. 13 cm

Answer 1

Answer:

D. 13 cm

$4 \pi (r+2)^2-4\pi r^2=704$

$4\pi(r^2+4r+4-r^2)=704$

$4\times \frac{22}{7} (4r+4)=704$

$4r+4=56$

$4r=52$

$r=52/4=13$