Question

A car travels at a speed of 80 km/h during the first half of its running time and at
40 km/h during the other half. Find the average speed of the car. (60 km/h) (AS,)
​

Answer 1

Answer:

Explanation:

Let the each half of the running time be t.

During first half time, speed of car is 80 km/h

Distance covered  d  

1

​  

=80t km

During second half time, speed of car is 40 km/h

Distance covered  d  

2

​  

=40t km

Total distance covered  d=d  

1

​  

+d  

2

​  

=80t+40t=120t

Total time taken   T=2t

Average speed   v  

avg

​  

=  

T

d

​  

=  

2t

120t

​  

=60 km/hr

Option C is correct

Answer 2

Given :

• Speed of 1st half journey (v1) = 80 km/h
• Speed of 2ns half journey (v2) = 40 km/h

To Find :

• Average speed of car

Solution :

⇒ v_(avg) = (2 * v1 * v2)/(v1 + v2)

⇒v_(avg) = (2 * 80 * 40)/(80 + 40)

⇒v_(avg) = (2 * 3200)/120

⇒v_(avg) = 6400/120

⇒v_(avg) = 53.333333

⇒v_(avg) ≈ 53.4 km/h

$\therefore$ Average speed of car is 53.4 km/h