1.  A salesman travels a distance of 50 km in 2 hours and 30 minutes. How much faster, in kilometres per hour, on an average, must he travel to make such a trip in 5/6 hour less time ?
A. 10
B. 20
C. 30
D. None of these

Answer: Option A

Explanation:

Time required = (2 hrs 30 min - 50 min) = 1 hr 40 min
                     = 1x(2/3) hrs

∴ Required speed = 50 x 3/5 km / hr = 30 km / hr.

∴ Original speed = 50 x 2/5 km / hr = 20 km / hr.

∴ Difference in speed = 30 - 20 km / hr = 10 km / hr.