A train covers a certain distance in 210 minutes at a speed of 60 kmph. The time taken by the train, to cover the same distance at a speed of 80 kmph is 

Train covers a certain distance in 210 minutes at a speed of 60 Kmph

total distance covered is 210 km

The time taken by the train to cover hte same distance at a speed of 80 kmpm is $\frac{210}{80}=\frac{21}{8} \mathrm{hours}$