Question

A car travels first 50 km with a constant speed of 30 km/h and next 40 km with a constant speed of 60 km/h . Caculate the average speed .

Answer 1

since equal distances are covered at 60 kmph and 40 kmph, we can apply the formula 2xy/(x+y)
Average speed=
2
×
40
×
60
40
+
60
2×40×6040+60 = 48 kmph

This formula works as follows

Let the distance to one side = x
Total distance = 2x

Time taken for the forward journey =
x
60
x60
Time taken for the return journey =
x
40
x40
Total time =
x
60
+
x
40
=
100
x
2400
x60+x40=100x2400

Average speed =
Total distance
Total Time
=
2
x
(
100
x
2400
)
Total distanceTotal Time=2x(100x2400) = 48 kmph