Question

Prashant cycled 100 m in 20 seconds. At this rate how long will it take him to go 1 km? What is his speed in km/h? What distance will he cover in 40 minutes?

Answer 1

Distance travelled by Prashant in 20 s = 100 m
∴ Distance travelled by Prashant in 1 s = 100/20
= 5 m
Speed of Prashant = 5 m/s

Now,
Time taken by Prashant to travel a distance of 5 m = 1 s
∴ Time taken by him to travel a distance of 1 km or 1000 m $=\frac{1}{5}\times 1000$
$=200\mathrm{s}$
Speed in km/h
5 m/s $=\frac{(5/1000)}{1/3600}$
$=18\mathrm{km}/\mathrm{h}$ (∵ 1 m = 1/1000 km and 1 s = 1/3600 h)

Again,

Distance covered in 1 s = 5 m
∴ Distance covered in 40 min or 2400 s = 5 $\times$ 2400
= 12000 m or 12 km

Therefore, Prashant will cover 12 kilometres in 40 minutes.