A student walks from his house at a speed of 21km per hour

A student walks from his house at
a speed of 2 1 km per hour and reaches his school
2
6 minutes late. The next day he increases his speed by 1 km per hour and reaches 6 minutes before school time. How far is the school from his house ?

Let the required distance be x km.
Difference of time

= 6 + 6 = 12 minutes =	1	hr.
	5

According to the question,

⇒	x	−	x	=	1	⇒	2x	−	2x	=	1
	5/2		7/2		5		5		7		5

⇒	14x − 10x	−	1
	35		5

⇒	4x	=	1	⇒ x =	35	=	7	km.
	35		5		20		4

Second Methdod :

Here, S₁ = 2	1	, t₁ = 6
	2

Here, S₂ = 3	1	, t₂ = 6
	2

Distance =	(S₁ ×S₂)(t₁ + t₂)
	S₂ −S₁

=	35	×	12	=	7	km
	4		60		4