The time taken by R to cover 45km is 1.2 hours. In how many seconds will he cover 400 metres?

First, let's calculate the speed of R:
Speed=
Time
Distance
​
=
1.2hours
45km
​
=37.5km/h
To convert speed from km/h to m/s, we multiply by
18
5
​
:

Speed=37.5×
18
5
​
m/s=
18
187.5
​
m/s=
6
62.5
​
m/s
Now, we need to find the time taken to cover 400 metres:

Time=
Speed
Distance
​
=
6
62.5
​

400
​
=
62.5
400×6
​
=
62.5
2400
​
=38.4seconds
Therefore, he will cover 400 metres in 38.4 seconds.