If a man starts at 7 a.m. at $\frac{5}{4}$ of his usual speed, he reaches office 30 minutes early than usual. So with a new speed at what time he reached his office?
Answer & explanation
Correct answer: option 3
We have,
Note, we know that if the distance is same then the ratio of speed will be inversely proportional to the ratio of time.
old new
Speed 4 5
Time 5 4 ( 1unit early)
1 unit = 30 min
4 units = 120 min or in 2 hours
So with a new speed at 7 + 2 = 9 am he reached his office.