Question

A CAR TRAVELS 120 miles from A th B at 30 mph but returns the same distance at 40 mph. What is the average speed for the round trip?
Please show steps
@Algebra I

Answer 1

\[\frac{120mi}{30mph}=4hr\]
\[\frac{120mi}{40mph}=3hr\]
\[4hr+3hr=7hr\]
\[\frac{120mi+120mi}{7hr}=\frac{240mi}{7hr}\approx 34.2857\frac{mi}{hr}\]
about 34.2857 mph

Answer 2

The total you have traveled 240 miles.

you travelled 120 miles at 40 mph in t1.

v=s/t

t1=120/40 =3hours

you travelled 120 miles at 30 mph in t2.


t2=120/30 =4 hours

so your average speed was total distance over total time spent. Thus

V_avrg = 240/(t1 +t2) = 240/7 = 34,2857143 mph