## Distance between two stations A and B is 778 km. A train covers the journey from A to B at 84 km per hour and returns back to A with a uniform speed of 56 km per hour. Find the average speed of train during the whole journey.

A. 60 km/hr

B. 30.5 km/hr

C. 57 km/hr

D. 67.2 km/hr

### Solution(By Apex Team)

The required average speed given by the formula, $\begin{array}{l}\text{ Average speed }\\ =\Large\frac{2xy}{x+y} \small\mathrm{~km}/\mathrm {hr}\\ \text{Where,}\\ \text{x=84 km/hr}\\ \text{y=56 km/hr}\\ \text{Average speed}\\ =\Large\frac {2 \times 84 \times 56}{84+56} \\ =67.2 \mathrm{kmph} \end{array}$

A. 20
B. 21
C. 28
D. 32

A. 18
B. 20
C. 24
D. 30

A. 10 years
B. 10.5 years
C. 11 years
D. 12 years