A train travels at a speed of 30 km/hr for 12 minutes and at a speed of 45 km/hr for the next 8 minutes. The average speed of the train for this journey is :

A. 30 km/hr

B. 36 km/hr

C. 37.5 km/hr

D. 48 km/hr

Answer: Option B

Solution(By Examveda Team)

Total distance travelled :
$$\eqalign{ & = \left( {30 \times \frac{{12}}{{60}} + 45 \times \frac{8}{{60{\text{ }}}}} \right){\text{ km}} \cr & = {\text{12 km}} \cr} $$
Total time taken :
= (12 + 8) min
= 20 min
= $$\frac{1}{3}$$ hr
∴ Average speed :
= (12 × 3) km/hr
= 36 km/hr