A boy travels between point A and point B at a speed of 6 km/h and returns at a speed of 9 km/h. If the total time taken by him is 1 hour 15 min, the distance between A and B is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 4.5 km
The distance is the same both ways, so the time going plus the time returning equals the total time, with each time found as distance ÷ speed. Let the distance be \(d\) km.
Total time: 1 hour 15 min \(\displaystyle =\frac{5}{4}\) h
\(\displaystyle \frac{d}{6}+\frac{d}{9}=\frac{3d+2d}{18}=\frac{5d}{18}\)
\(\displaystyle \frac{5d}{18}=\frac{5}{4}\)
\(\displaystyle d=\frac{18}{4}=4.5\) km