Question

SSC Test Questions

A motorist covers a distance of 39km in 45min by moving at a speed of x kmph for the first 15min, then moving at double the speed for the next 20 min, and then again moving at his original speed for the rest of the journey. Find x ?

Answer 1

total distance = 39 km
total duration = 45 min = 45/60 = 3/4 hour

x kmph for 15 min => distance travelled = 15/60 * x = x/4 km
2 x kmph for 20 min => distance travelled = 20/60 * 2x = 2x/3  km
x kmph for  (45 - 20 -15) min => distance = 10/60 * x = x/6  km

total distance = x/4 + 2x/3 + x/6 = x [ 1/4 + 2/3 + 1/6 ] = 13/12 * x
                   13/ 12 * x = 39 km

                   x = 39/13 * 12 = 36 kmph