A bus covers a distance of 45 km in 45 minutes. If its speed is decreased by 20km/hr, then what will the time taken by it to cover the same distance?

67.5 minutes

Speed of the bus = $\frac{distance}{time}$

                         = $\frac{45}{\frac{45}{60}}$ = 60km/hr

Decreased speed = 60 - 20 = 40 km/hr

Time taken to cover 45km by this speed = $\frac{distance}{speed}$

                           =  $\frac{45}{40}$ = 1.125 hr

                           = 1.125 x 60 = 67.5 minutes