P and Q starting simultaneously from two different places

P and Q starting simultaneously from two different places proceed towards each other at a speed of 20 km/hour and 30 km/hour respectively. By the time they meet each other. Q has covered 36 km more than that of P. The distance (in km.) between the two places is

Let P and Q meet after t hours.
Distance = speed × time
According to the question,
30t – 20t = 36
⇒ 10t = 36

⇒ t =	36	= 3.6 hours
	10

∴ Distance between P and Q
= 30t + 20t
= 50t = (50 × 3.6) km.
= 180 km.

Second Method :
Here, a = 30, b = 20, d = 36

Required distance =		a + b		× d
		a − b

=		30 + 20		× 36
		30 − 20

=	50	× 36 = 180 km
	10