Question

On a journey across Bombay, a tourist bus averages 10 km/h for 20% of the distance, 30 km/h for 60% of it and 20 km/h for the remainder.

Answer 1

Solution:
Let X be the total distance and Y be the average speed.

Time t1 = 0.2X/10
Time t2 = 0.6X/30
Time t3 = 0.2X/20
& Total Time T = X/Y .....E1
Also since, Total Time T = t1 + t2 + t3 ....E2

Therefore, from E1 & E2
(0.2X/10) + (0.6X/30) + (0.2X/20) = X/Y

or {0.2X(30*20) + 0.6X(20*10) + 0.2X(30*10)} / 10*30*20 = X/Y

or (120X + 120X + 60X) / 6000 = X/Y

or 300X/6000 = X/Y

or X/20 = X/Y

Therefore, Y = 20.
Hence, the average speed of the tourist bus is 20 km/hr.

Answer 2

Answer:

Step-by-step explanation:

TOTAL 100% JORNEY.

=100/(20/10km/h)+(60/30km/h)+(20/20km/h)

=100/5

=20km/h ANS