What will be the train’s average speed over the entire journey?

Question

A train covers its outward journey at 81 mph.
It returns, over exactly the same distance at 64.8 mph.

What will be the train’s average speed over the entire journey?

Answer 1

Its 72 MPH.

Answer 2

let train covers outword journey=81 miles
then total distance train covers=81+81=162 miles
total time=1+(81/64.8)
=2.25
average speed =total speed/total distance/total time
=162/2.25
=72mph

Answer 3

A train covers its outward journey at 81 mph.
And returns, over exactly the same distance at 64.8 mph
so average speed of train = (2*81*64.80)/81+64.8
=10497.6/145.8
=72 mph