Two trains of lengths $120 \,m$ and $80 \,m$ are running in the same direction with velocities of $40 \,km/h$ and $50 \,km/h$ respectively. The time taken by them to cross each other is (in $sec$).

$A$ person covers a certain distance in $6 \, hours$ if he travels at $40 \, km/h$. If he has to cover the same distance in $4 \, hours$,then his speed must be (in $km/h$):

$A$ train $200 \, m$ long is running at a speed of $20 \, m/s$. In how much time (in $seconds$) will it cross a bridge of $400 \, m$ length?

$A$ man travelled a certain distance by train at the rate of $25 \text{ km/h}$ and walked back at the rate of $4 \text{ km/h}$. If the whole journey took $5 \text{ h } 48 \text{ min}$,what is the distance? (in $\text{km}$)

$A$ car travels $20\%$ slower than a train. Both start from point $A$ at the same time and reach point $B$ $240\, km$ away at the same time. On the way,the train takes $48\, minutes$ for stopping at stations. What is the speed (in $km/hr$) of the car?

$A$ bus moving at a speed of $45 \, km/h$ overtakes a truck $150 \, m$ ahead going in the same direction in $30 \, s.$ The speed of the truck is? (in $km/h$)