Without any stoppage average speed of a train is 90 km/hr and with stoppage average speed reduces to 80 km/hr . Find the total time of stoppage in total 3 hours .

20 min

Distance = Speed × Time

Distance covered by train without any stoppage in 3 hours = 90 km/hr × 3 hr 

= 270 km

But it travelled = 80 km/hr × 3 hr  = 240 km 

Time taken to travel 240 km without stoppage = \(\frac{240}{90}\)

 = \(\frac{24}{9}\) hours

Difference in time = 3 - \(\frac{24}{9}\)= \(\frac{1}{3}\) hour = 20 min 

Total time of stoppage in 3 hours is 20 min .