The speed of the bus 54 km/hr excluding stoppage and 45 km/hr including stoppages. For how many minutes does the bus stop per hour

L.C.M of 54 and  $45=270$

$\therefore$time taken by bus to cover 270 km

excluding stoppages  $=\frac{270}{54}=5hrs$

Time taken by the bus to cover 270 km

Including stoppages  $=\frac{270}{45}=6hrs$

$\therefore$Time for which the bus stops

Per hour  $=\frac{6-5}{6}\text{hours}=\frac{1}{6}\times 60\min =10\min$