What is the radius of a normal cylinder whose height is 21 cm and curved surface area is 1386 cm2?

10.5 cm 3.5 cm 7 cm 10 cm

10.5 cm

We know that, The curved surface area of the cylinder = C.S.A = 2πrh We have, H = 21 cm C.S.A = 1386 cm2 = 1386 = 2 × \(\frac{22}{7}\) × r × 21 = 1386 = 2 × 22 × 3 × r = r = 10.5