A car travels 120 miles in 7 hours. What is its average speed?

The average speed is 17.142857 mph.

v = \frac{d}{t} = \frac{120}{7} = 17.142857\ \text{mph}

How to work it out

1
Write down what you know: distance d = 120 miles, time t = 7 hours. You are asked for the speed v.
2
Use the formula speed = distance ÷ time:
$v = \frac{d}{t} = \frac{120}{7} = \frac{120}{7} = 17.142857$
3
Answer with the unit: 17.142857 mph.
4
The same formula rearranged: distance = speed × time (17.142857 × 7 = 120 miles) and time = distance ÷ speed (120 ÷ 17.142857 = 7 hours).

LaTeX source of the formulas on this page

\[ v = \frac{d}{t} = \frac{120}{7} = 17.142857\ \text{mph} \]
\[ v = \frac{d}{t} = \frac{120}{7} = \frac{120}{7} = 17.142857 \]

What is the speed if a car travels 120 miles in 7 hours?

The average speed is 17.142857 mph.

How far does it go in 3 hours at that speed?

51.428571 miles.