The wheels of the locomotive of a train are 2.1 m in radius.

Radius of the wheel = 2.1 m

Circumference of the wheel $=2 \pi \mathrm{r}$

$=2 \times \frac{22}{7} \times 2.1$

$=13.2 \mathrm{~m}$

Distance covered by the wheel in 1 revolution = 13.2 m

Distance covered by the wheel in 75 revolutions $=(13.2 \times 75)=\left(990 \times \frac{1}{100}\right) \mathrm{m}$

$=\left(990 \times \frac{1}{1000}\right) \mathrm{km}$

Distance covered by the wheel in 1 minute = Distance covered by the wheel in 75 revolutions $=\frac{990}{1000} \mathrm{~km}$

$\therefore$ Distance covered by the wheel in 1 hour $=\frac{990}{1000} \times 60$

$=59.4 \mathrm{~km} / \mathrm{h}$