## 1 Answer

total distance / total time

If \(\mathrm{x}\) is the distance from \(\mathrm{A}\) to \(\mathrm{B}\), then the total distance is equal to \(2 \mathrm{x}\) (away and return). The tota

T time is equal to time \(t 1=x / 40\) from \(A\) to \(B\) (away) plus \(t 2=x / 60\) from \(B\) to \(A\) (return). Hence

\(T=x / 40+x / 60=100 x / 2400=x / 24\)

The average speed is given by

\(2 x /(x / 24)=48 \mathrm{mph}\)