Question

Macleod drove from Bayside to Chatham at a constant speed of $21$ miles per hour and then returned along the same route from Chatham to Bayside. If her average speed for the entire journey was $26.25$ miles per hour, calculate at what average speed, in miles per hour, did Macleod return from Chatham to Bayside.

• A. $28$
• B. $31$
• C. $31.5$
• D. $35$
• E. It cannot be determined from the information given

Answer 1

The correct option is C $31.5$

Let the Macleod return from Chatham to Bayside by average speed x miles per hour.

Then average speed from total journey for both sides $=$ $\frac{x+21}{2}$

But total average speed for both side is given $26.25$ miles per hour

$\therefore \frac{x+21}{2}=26.25$

$\Rightarrow x+21=52.5$

$\Rightarrow x=52.5-21=31.5$