Priya's brother leaves home walking at 5 km/h. Ten minutes later Priya follows on a bicycle at 15 km/h along the same road. How long after she sets off does she catch him?

Explanation

1. 01

   In 10 min her brother walks $5 \times \frac{1}{6} = \frac{5}{6}$ km.

2. 02

   Priya gains at $15 - 5 = 10$ km/h.

3. 03

   Time $= \frac{5/6}{10} = \frac{1}{12}$ $h = 5$ min.