Puzzle 25) Bus and its speed

Puzzle

A bus after travelling 50 km from A faces an accident and proceeds at 4/5th of the initial speed and reaches its destination 45 minutes late. Had the accident happened 20 km. further, it would have arrived 12 min. sooner. Find the original speed and the distance of the bus.

Important points of puzzle (Key points):

1. A Bus is travelling 50 km from A.
2. It faces an accident and proceeds at 4/5th of the initial speed
3. It reaches its destination 45 minutes later.
4. If accident happen 20 km it would arrive 12 minutes sooner.
5. Find original speed and distance of the bus.

Answer

The original speed of the bus is 25 km/hour and its distance is 125 kilometers.

Reason

Let the speed be x km/hour.
When the bus travels with its usual speed throughout, it reaches 45 minutes earlier than after reducing the speed to 4/5th after 50 kilometers.
When the bus travels with its usual speed throughout, it reaches 33 (45 – 12) minutes earlier than after reducing the speed to 4/5th after 70 kilometers.
When the speed becomes 4/5th of the usual, time taken would become 5/4th the usual, i.e. 1/4th more of the usual time.
So, 1/4th of the usual time taken to travel CB = 45min.
1/4th of the usual time taken to travel CD (i.e. 20 km) = 12 min.
Usual time to travel 20 km. = 48 min.
Usual Speed = 20 * 60/48 = 25 km/hours.
Usual time taken to travel CB = 45 * 4 = 3 hours.
Distance CB = 25 * 3 = 75 km.
Total distance = 50 + 75 = 125 km.
Hence the correct answer is 25 kilometers/hour and 25 kilometers.