A car has to cover the distance 60 km, if half of the total time it travels with velocity 80 km/h and in rest half time its speed becomes 40 km/h, the average speed of car will be,

 (a) 60 km/h 

(b) 80 km/h 

(c) 120 km/h 

(d) 180 km/h 

How do we solve this question?

Given: Total distance = 60 km. Half the total time at 80 km/h, remaining half at 40 km/h.

Step 1: Average speed formula

Average Speed = Total Distance / Total Time

Step 2: Let total time be 2t

• Time at 80 km/h = t hours
• Time at 40 km/h = t hours

Step 3: Distance covered in each half

• Distance at 80 km/h: 80 × t = 80t km
• Distance at 40 km/h: 40 × t = 40t km

Total distance = 80t + 40t = 120t

Step 4: Match with actual distance

Given total distance is 60 km, so:

120t = 60 ⇒ t = 0.5 h

Hence, total time = 2t = 1 h

Step 5: Compute average speed

Average Speed = 60 km / 1 h = 60 km/h

Final Answer: (a) 60 km/h