The height of a right circular cylinder is 10.5 cm. If three times the

1.	The height of a right circular cylinder is 10.5 cm. If three times the sum of the areas of its two circular faces is twice the area of the curved surface area. Find the radius of its base.
Answer» We have, Height of cylinder = 10.5 cm Let radius of cylinder be ‘r’ cm So, Area of two bases of cylinder = 2πr² Area of curved surface of cylinder = 2πrh Now, 3 (2πr²) = 2 (2πrh) 6πr² = 4πrh πr²/ πr = 4/6 h r = 2/3 h = 2×10.5 /3 = 7cm ∴ Radius of base of cylinder is 7cm.

The height of a right circular cylinder is 10.5 cm. If three times the sum of the areas of its two circular faces is twice the area of the curved surface area. Find the radius of its base.

Answer»

We have,

Height of cylinder = 10.5 cm

Let radius of cylinder be ‘r’ cm

So,

Area of two bases of cylinder = 2πr²

Area of curved surface of cylinder = 2πrh

Now,

3 (2πr²) = 2 (2πrh)

6πr² = 4πrh

πr²/ πr = 4/6 h

r = 2/3 h

= 2×10.5 /3

= 7cm

∴ Radius of base of cylinder is 7cm.