Question:
The radii of the top and bottom of a bucket of slant height 45 cm are 28 cm and 7 cm, respectively. The curved surface area of the bucket is
(a) 4950 cm2
(b) 4951 cm2
(c) 4952 cm2
(d) 4953 cm2
Solution:
(a) Given, the radius of the top of the bucket, R = 28 cm
and the radius of the bottom of the bucket, r = 7 cm
Slant height of the bucket, l= 45 cm
Since, bucket is in the form of frustum of a cone.
∴ Curved surface area of the bucket = π l (R + r) = π x 45 (28 + 7)
$[\because$ curved surface area of frustum of a cone $=\pi(R+r) l]$
$=\pi \times 45 \times 35=\frac{22}{7} \times 45 \times 35=4950 \mathrm{~cm}^{2}$