Akhil takes 30 minutes extra to cover a distance of 150 km if he drives 10 km/h slower than his usual speed. How much time will he take to drive 90 km if he drives 15 km per hour slower than his usual speed?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 2 h
Let the usual speed be 'x' km/hr.
According to the question,
⇒ 150/(x - 10) - 150/x = 30/60
⇒ 150 (10) × 2 = x(x - 10)
⇒ x2 - 10x -3000 = 0
⇒ (x - 60)(x - 50) = 0
⇒ x = 60, -50.
Time taken by Akhil to cover 90 km at the speed of 60 - 15 = 45 km/hr.
Time = 90/45 = 2 hours.