Suresh drives his car to a place 150 km away at an average speed of 50 km/hr and returns
at 30 km/hr. What is his average speed for the whole journey ?
If a car covers a certain distance at x kmph and an equal distance at y kmph. Then,
the average speed of the whole journey =
2
x
y
x
+
y
kmph.
By using the same formula, we can find out the average speed quickly
average speed =
2
×
50
×
30
50
+
30
=
2
×
50
×
30
80
=
2
×
50
×
3
8
=
50
×
3
4
=
25
×
3
2
=
75
2
=
37.5
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