Question

8. Travelling from his house at 30 kmph, a person is
late to his office by 5 minutes. If he increases his
speed by 10 kmph, he would be early by 15 minutes
to his office. What should be his speed so that he
reaches his office on time?
(A) 36 kmph
(8) 32 kmph
(C) 34 kmph
(D) 35 kmph​

Answer 1

Answer:

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Step-by-step explanation:

Let the distance between his house and office is x kms. and speed so that he

reaches his office on time is y km/hr.

Reaching time from house to office = x/y hrs.

Reaching time @ 30km/hr = x/30 hrs. , accordingly :-

x/30 - x/y = 5/60. , or, x/30 - x/y = 1/12………………(1).

Reaching time @ (30+10)= 40km/hr. = x/40 hrs. , accordingly :-

x/y - x/40 = 15/60 , or, x/y - x/40 = 1/4…………………….(2)

Adding eqn.(1) & eqn.(2).

x/30 -x/40 = 1/12+1/4.

or, x/120 = 1/3 =>. x= 120/3 = 40 km.

Putting x=40 in eqn.(1).

40/30 - 40/y = 1/12.

or, 4/3 - 1/12 = 40/y.

or, 15/12 = 40/y =>. y = 32 kmph.

So,the answer is 32 km/hr

It is option (B) 32 kmph

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