Amit walks at a uniform speed of 4 km/h and 4 h after his start, Brijesh cycles after him at the uniform rate of 20 km/h. How far from the starting point will Brijesh catch Amit?

Let Brijesh Catches Amit after x h.
Then, distance travelled by Amit in (x + 4) h = Distance travelled by Brijesh in x h.
According to the question,
4(x + 4) = 20 x
⇒ 4x + 16 = 20x
⇒ 16x = 16
∴ x = 16/16 = 1
Distance travelled by Brijesh in1h = 1 x 20 = 20 km