Question

The train runs for 2 ½ hours at a speed of 62 km/hr and at a speed of 68 km/hr for 1 ¼ hour. Find the average speed of a train

A. 55 km/hr 

B. 64 km/hr

C. 62 km/hr

D. 70 km/hr

1. A
2. D
3. C
4. B

Answer 1

Correct Answer - Option 4 : B

Given:

Ran for 5/2 hours at 62km/hr, and for 5/4 hours at 68 km/hr 

Formula Used:

Speed = Distance/Time

Average speed = Total distance traveled/Total time taken

Calculation:

In the first case,

⇒ 62 = Distance/(5/2)

⇒ Distance = (62 × 5)/2

⇒ Distance = 155 km

In the second case,

⇒ 68 = Distance/(5/4)

⇒ Distance = (68 × 5)/4

⇒ Distance = 85 km

Using the formula for average speed,

Average speed = (155 + 85)/(5/2 + 5/4)

⇒ Average speed = 16 × 4

∴ The average speed of a train is 64 km/hr