Question 1153814
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Two responses you have received at this point have shown finding the average speed as total distance divided by total time:<br>
{{{total distance/total time = 400/((200/56)+200/37))}}}<br>
That is an ugly kind of calculation that I prefer to avoid.<br>
This is how I would solve the problem.<br>
The ratio of speeds is 56:37; since the distances are the same, the ratio of times is 37:56.<br>
That means the truck driver travels at 56mph for 37/(56+37) of the time and at 37mph for 56/(56+37) of the time.  The average speed is then the WEIGHTED average<br>
{{{(37/(56+37))*56+(56/(56+37))*37 = (2*37*56)/(56+37)}}} = 44.56 to 2 decimal places<br>
That to me is an easier calculation for finding the answer.<br>
Note that that calculation is exactly what the other tutor @ikleyn shows in her response: for a round trip at two different speeds, the average speed is<br>
{{{(2(v(1))(v(2)))/(v(1)+v(2))}}}<br>
Note that one reason this calculation is easier is that it does not use the given distance.  The average speed is independent of the distance -- a point tutor @ikleyn also makes in her response.<br>
So if you were (or are) in a situation where you need to do this kind of calculation frequently, the easiest thing to do is memorize the formula and use it....<br>