Question

By increasing the speed of a car by 10 kilometre per hour the time of journey for the distance of 72 kilometre is reduced by 36 minutes find the original speed of the car​

Answer 1

Answer:

s=d/t

so s =x (say)

x=72/36 = 2 so 2 km/h is original speed

Answer 2

Answer :

30 km/h

Explanation :

Let the initial time taken to cover 72km be T1 & speed be S1

Also, T2 be new time & S2 be new speed.

T1 = 72/S1

T2 = 72/(S1+10)

According to question:

T1 - T2 = 36/60

OR, (72/S1) - 72/(S1+10) = 36/60

OR, 2/S1 - 2/(S1+10) = 1/60

OR, 120[S1+10-S1] = 1

------------------------

S1(S1+10)

Now,

S1^2 +10S1 = 1200

S1 = 30 or -40 ----> ( not possible)

So original speed = 30 km/h