Question

2) Two hemispherical depressions of radius 7 cm are made at the two ends of a cylindrical log
of wood of height 15 cm and radius 10.5 cm. Find the total surface area of the remaining solic
tent is of the shape of a right circular cylinder unt​

Answer 1

Step-by-step explanation:

Radius of each hemisphere = r = 7 cm

Height of total solid = 104 c

Height of cylinder, h=104−2×7=90cm

Then,

T.S.A. of the solid = C.S.A. of the cylinder + 2 × C.S.A. of the hemisphere 

=2πrh+2×2πr2

=2πr(h+2r)

=2×722×7(90+2×7)

=44×104

=4576cm2

=0.4576m2

∴ Total surface of the given solid is 0.4576 m2.

Cost of polish is Rs. 100 per sq. mtr.

∴ Cost of polishing the solid of area 0.4576m2=0.4576×100=45.76

Total cost of polish is Rs. 45.76.