A train running at a speed of 64 km/h takes 50 min to travel a certain distance. By how much should it increase its speed (in km/h) to travel the same distance in 40 min?

Correct option is C

Using the formula:
Distance = Speed × Time 
Convert 50 minutes to hours:
50 min = 50/60 = 5/6 hours
Now, calculate the distance:
Distance = 64 × 5/6
= 320/6 = 160/3 km)
Find the Required Speed Let the new speed be V km/h and time be 40 minutes (i.e., 2/3 hours). Using the same formula:
Distance = V × 2/3
Since the distance remains the same:
160/3 = V × 2/3
Multiply both sides by 3/2:
V = 160/3 × 3/2
V = 160/2 = 80 km/h
Increase in speed = 80 – 64 = 16 km/h