Question

Find the area of base and radius of a cylinder if its curved surface area is 660sq.cm and height is 21 cm.​

Answer 1

Answer:

Area of base of a cylinder is 78.6 cm² .

Step-by-step explanation:

Formula

$Curved\ surface\ area\ of\ a\ cylinder =2\pi$

$Area\ of\ base\ of\ cylinder = \pi r^{2}$

Where r is the radius and h is the height of the cylinder .

As given

Curved surface area is 660 cm² and height is 21 cm .

$\pi = \frac{22}{7}$

Put in the formula

$660 =2\times \frac{22}{7}\times r\times$

×r×21

660 = 2 × 22× r × 3

660 = 132r

$r = \frac{660}{132}$

r = 5 cm

Thus radius of cylinder is 5 cm .

Put in the formula

$Area\ of\ base\ of\ cylinder = \frac{22}{7}\times 5\times$

$Area\ of\ base\ of\ cylinder = \frac{22\times 5\times 5}{7}$

$Area\ of\ base\ of\ cylinder = \frac{550}{7}$

= 78.6 cm² (Approx)

Therefore the area of base of a cylinder is 78.6 cm² .

Answer 2

Answer:

let r is the radius of the base of the cylinder

so, it's curved surface area =2πr.height

2π.r.h=660

=> 2.π.r.21=660

=> π.r=660/2.21

=> 22/7.r=330/21

=> r =330×7/21×22

=> r=110/22

=> r=5

so radius of the cylinder=5 cm

area of the base=π.r^2=22×5^2/7 sq cm

=22×25/7 sq cm

=550/7sq cm

=78 4/7 sq cm