How many bullets, each of diameter 1.5 cm, can be made by melting a cylinder of lead having radius of the base 5 cm and height 18 cm ?

Bullet is in shape of sphere.

Radius of bullet, r = $\dfrac{\text{diameter}}{2} = \dfrac{1.5}{2}$ = 0.75 cm

Radius of cylinder, R = 5 cm

Height of cylinder, h = 18 cm

Given, bullets are made by melting a cylinder of lead.

∴ Volume of cylinder = n × Volume of each bullet

$\Rightarrow π \text{R}^2 \text{h} = \text{n} \times \dfrac{4}{3} π \text{r}^3 \\[1em] \text{Divide by π on both sides, we get:} \\[1em] \Rightarrow \text{R}^2 \text{h} = \text{n} \times \dfrac{4}{3} \text{r}^3 \\[1em] \Rightarrow 5^2 \times 18 = \text{n} \times \dfrac{4}{3} \times 0.75^3 \\[1em] \Rightarrow 25 \times 18 = \text{n} \times \dfrac{4}{3} \times 0.421875 \\[1em] \Rightarrow 450 = \text{n} \times 0.5625 \\[1em] \Rightarrow \text{n} = \dfrac{450}{0.5625} \\[1em] \Rightarrow \text{n} = 800.$

Hence, 800 bullets are made.