Question

If a car travels a distance with 20% less speed, then it will reach 15 minutes late. What is the usual time (in minutes) taken by the car to travel the same distance?

Answer 1

Answer:

60 mins

Explanation:

If a car travels a distance with 20% less speed, then it will reach 15 minutes late. What is the usual time (in minutes) taken by the car to travel the same distance?

Let say Distance = D

Normal Time = T

Speed = D/T

Speed reduced by 20% means

Speed = D/T ( 1  - 20/100)  =  0.8D/T

New time taken = D/(0.8D/T)  = T/0.8  = 1.25T

1.25T - T = 15 min

=> 0.25T = 15 min

=> T = 60 min

Usual time = 60 mins

Answer 2

Answer:

60 minutes

Let the usual time be 't' minutes and speed be x , then xt = 0.8x*(t+15)

t = 0.8t + 12

0.2t = 12 or t=60