Question

a car travelled 60Km to the north of Patna and then 90Km to the south from there. how far from Patna was the car finally

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
= 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

Time taken for the return journey =
x
40

Total time =
x
60
+
x
40
=
100
x
2400


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


Hope this will help you...... ✌