Question

A car travels from A to B at a speed of 40 mph then returns, using the same road, from B to A at a speed of 60 mph. What is the average speed for the round trip?

Answer 1

Answer:

48mph

Step-by-step explanation:

$S_{1}$$=\frac{d} {t_{1} }$$=40=\frac{d}{t_{1} }$

=$\frac{d}{S_{1} } =t_{1}$..........(1)

$S_{2}=\frac{d}{t_{2} }$$=60=\frac{d}{t_{2}}$

$\frac{d}{S_{2} } =t_{2}....(2)$

$S_{av} =\frac{total distance}{total time}$

$=\frac{d+d}{\frac{2d+3d}{120} }$.....from eq 1 and 2

$=2d*\frac{120}{5d}$

$therefore, S_{av}=48m/s$

(*= mutiplication)

Answer 2

Answer:

Let distance between A and B be "x" units. So average speed will be = total distance/total time taken.

Step-by-step explanation:

Total distance = 2x.

Total time = x/40 + x/60, which is = 5x/120.

Now, average speed = 2x/ (5x/120)

Which is 240x/5x = 48 mph.

This means it's less than 50 mph.