Question

Q 7A conical block of silver has a height of 16 cm and base radius of 12 cm ,the silver is melted to form coins of 1/6 cm thick and 3 /2 cm in diameter . Find the no of coins to be made

Answer 1

$let \: first \: find \: volume \: of \: conical \: block$

$volume \: of \: conical \: block \: = \: \frac{1}{3} \times \pi {r}^{2} h$

$= \frac{1}{3} \times 3.14 \times 12 \times 12 \times 16$

$= 3.14 \times 4 \times 12 \times 16$

$= 2411.52 {cm}^{3}$

$now \: we \: will \: find \: volume \: of \: coin$

$volume \: of \: coin \: = \pi {r}^{2} h$

$r = \frac{d}{2}$

$r = \frac{3}{2} \times \frac{1}{2}$

$r = \frac{3}{4}$

$volume \: of \: coin = 3.14 \times \frac{3}{4} \times \frac{3}{4} \times \frac{1}{6}$

$= 3.14 \times \frac{9}{8} \times \frac{1}{6}$

$= 3.14 \times \frac{3}{8} \times \frac{1}{2}$

$= 3.14 \times \frac{3}{16}$

$= 0.58875$

$≈0.59$

$number \: of \: coins = \frac{2411.52}{0.59}$

$≈40coins$