Question 1197471
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I definitely agree with tutor @Math_tutor2020 that it is better to solve the problem by a method that you understand, rather than by blindly plugging numbers into a magic formula.<br>
Here is an informal solution method that is similar to his, yet very different.<br>
The ratio of the two speeds is 24:16 = 3:2, and the distances there and back are the same.  That means the ratio of the times at the two speeds is 2:3.<br>
So 2/5 of the total time is spent at 24mph and 3/5 of the total time is spent at 16mph.  The average speed in mph is then<br>
{{{(2/5)(24)+(3/5)(16)=48/5+48/5=96/5}}}<br>
ANSWER: 96/5 = 19.2 miles per hour<br>