Let the distance from Delhi to Gurgaon be ‘d’ km. The first 30 km he travels at his usual speed. However, the remaining ‘d-30’ km he travels at a reduced speed.
To travel ‘d’ km he usually takes T hr. Therefore, to travel ‘d - 30’ km he should ideally take hr. However, this is only if he travels at his usual speed. It is given that he traveled only at of his usual speed. Because of this he would have taken of the time to travel the remaining distance, i.e., he takes of the time extra. This is given to be 45 minutes (or hr)
........(1)
On the other hand, had the same thing happened after he travelled 48 km, he would have reached only 36 minutes or hrs late. Hence,
........(2)
Dividing (1) by (2) and solving for d, we get d = 120 km.
Answer choice (b)
Correct Answer: 120 km