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

A student starting from his house walks at a
speed of 2 1 km/hour and reaches his
2
school 6 minutes late. Next day starting at
the same time he increases his speed by 1 km/hour and reaches 6 minutes early. The distance between the school and his house is

Distance between school and house = x km (let)

Time =	Distance
	Speed

According to the question,

x	−	x	=	6 + 6	=	1
5/2	−	7/2	=	60	=	5

(Difference of time = 6 + 6 =12 minutes)

⇒	2x	−	2x	=	1
	5		7		5

⇒	14x − 10x	=	1	⇒	4x	=	1
	35		5		35		5

⇒ 4x =	35	= 7
	5

⇒ x =	7	= 1	3	km.
	4		4

Second Method :

Here, S₁ = 2	1	, t₁ = 6
	2

S₂ = 3	1	, t₂ = 6
	2

Distance =	(S₁ × S₂)(t₁ + t₂)
	S₂ − S₁

=	35	×	12
	4		60

=	7	= 1	3	km
	4		4