Question 1196983
<br>
The solution method from the other tutor uses the basic definition of average to find the answer.  That method is of course fine.<br>
If the numbers being averaged are close together, a different solution method, comparing each number to the desired average, is often easier, because the numbers you have to work with are smaller.<br>
For this example....<br><pre>
  49:  -2
  57:  +6
  50:  -1
  51:   0
 ---------
  sum: +3</pre>
Over the first four days, he is 3 miles over what he needs to get an average of 51 miles per day; so on the last day he can be 3 miles short of the desired average.<br>
ANSWER: 51-3 = 48 miles<br>