A covered a distance of 240 km at a certain speed. had his speed been 8 km/h less, then the time taken would have been an hour more for covering the same distance, How much time (in hours) will he take to cover a distance of 480 km at his original speed?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 10
Let the initial speed be x km/hr
240/(x - 8} - 240/x = 1
On solving further we get,
⇒ x2 - 8x - 1920 = 0
⇒ x2 - 48x + 40x - 1920 = 0
⇒ x(x - 48) + 40(x - 48) = 0
⇒ (x - 48)(x + 40) = 0
⇒ x = 48, -40
Time taken by A to cover a distance of 480 at the speed of 48 km/hr
= 480/48 = 10 hours.