M4maths Previous Puzzles

27 Jul 2022 Time Distance & Speed

A bus takes 1 hour 20 minutes more to travel a distance of 210 km, if its speed is reduced by 10 km/hr than actual speed, then find the time taken to cover a distance of 300 km at double the usual speed.

OPtion

1) 6 hours 40 minutes
2) 4 hours 20 minutes
3) 3 hours 40 minutes
4) 4 hours 40 minutes
5) 6 hours 20 minutes
6) 3 hours 20 minutes
7) 2 hours 20 minutes
8) 1 hours 40 minutes
9) 2 hours 40 minutes
10) None of these

Solution

Let the usual speed of a bus=x km/h
Then, 210/(x-10) - 210/x = 4/3
x² - 10x - 1575 = 0
(x-45) (x+35) = 0
x=45
.'. Time taken to cover 300 km at 90 km/h = 300/90 hrs = 3⅓ hrs = 3 hrs 20 min.
Correct Option 6)

Correct Option: 6 Best Solution (1)