Question

Tick (✓) the correct answer:
The number of coins, each of radius 0.75 cm and thickness 0.2 cm, to be melted to make a right circular cylinder of height 8 cm and base radius 3 cm is
(a) 460
(b) 500
(c) 600
(d) 640

Answer 1

(d) 640
$\mathrm{Total}\mathrm{no}.\mathrm{of}\mathrm{coins}=\frac{\mathrm{volume}\mathrm{of}\mathrm{cylinder}}{\mathrm{volume}\mathrm{of}\mathrm{each}\mathrm{coin}}=\frac{\mathrm{\pi }\times 3\times 3\times 8}{\mathrm{\pi }\times 0.75\times 0.75\times 0.2}=640$