Question

Two buses start from a bus terminal with a speed of 20 km/h at interval of 10 minutes. what is the speed of a man coming from the opposite direction towards the bus terminal if he meets the buses at interval of 8 minutes

Answer 1

Let the speed of the man be
x
x km/hr

Speed is inversely proportional to the time (when distance is constant).
Here the distance between the buses remains constant.

20 kmph is inversely proportional to 10 minutes
(20+x) kmph is inversely proportional to 8 minutes

⇒
20×10=
(
20
+
x
)
×
8
200
=
160
+
8
x
40
=
8
x
x
=
5