Question

a bus left delhi at 1 pm sharp . three hours later another bus started from delhi in the same direction. The second Bus overtook the first bus at 10 pm. Find the average speed of the two busses over this journey if the sum of there speed is 100 km/h

Answer 1

Given:

Bus 1 left Delhi at 1 pm

Bus 1 and Bus 2 both come at same place at 10 pm.

Sum of their speeds = 100 km/hr

To find:

The average speed of the two buses.

Solution:

Let the speed of bus 1 = x

Then speed of bus 2 = 100-x

Distance travelled by bus 1 from 1 pm to 10 pm = speed/ time

= x/ 9 km

Distance travelled by bus 2 from 4 pm to 10 pm = speed/ time

= (100-x)/ 6 km

Since the distance is same for both the buses:

x/9 = (100-x)/6

x/3 = (100-x)/2

2x = 300 - 3x

5x = 300

x = 30 km/hr

Speed of bus 2 = 100-x = 100-30 = 70 km/hr

Average speed of bus 1 = 30 km/hr.

Average speed of bus 2 = 70 km/hr.