Question

One day Prakash started late for office by 1 hour, so he increased his normal speed by 5 km/hr so that he reaches on time. Find the normal time taken to reach his office if his office is at a distance of 60 km from his house.

• A. 3 hrs
• B. 5 hrs
• C. 6 hrs
• D. 4 hrs

Answer 1

The correct option is D

4 hrs

Take a middle answer option, say 5 hours

Normal speed = 60/5 = 12 kmph

Speed increased to 12 + 5 = 18 kmph.

60/18 = 3.33 hours, the difference is more than 1 hour. This is not the answer.

We can also eliminate 6 hours, as that will result in a higher time difference.

Answer is either 3 or 4 hours (answer is close to 5)

Trying for 4 hours,

Normal speed = 60/4 = 15 kmph

Speed increased to 20 kmph

60/20 = 3. 4 – 3 = 1. This is the answer. Option (d)