Question

The diameter of the wheel of a car is 77 cm. How many revolutions will it make to travel 121 km?

Answer 1

Diameter of the wheel = 77 cm
⇒ Radius of the wheel = $\left(\frac{77}{2}\right)$ cm
Circumference of the wheel = $2\mathrm{\pi r}$
= $\left(2\times \frac{22}{7}\times \frac{77}{2}\right)$cm = (22 × 11) cm = 242 cm
= $\left(\frac{242}{100}\right)$m = $\left(\frac{121}{50}\right)$m
Distance covered by the wheel in 1 revolution = $\left(\frac{121}{50}\right)$ m
Now, $\left(\frac{121}{50}\right)$ m is covered by the car in 1 revolution.
(121 × 1000) m will be covered by the car in $\left(1\times \frac{50}{121}\times 121\times 1000\right)$ revolutions, i.e. 50000 revolutions.
∴ Required number of revolutions = 50000