A car travels 80 miles in 9 hours. What is its average speed?

The average speed is 8.8888889 mph.

v = \frac{d}{t} = \frac{80}{9} = 8.8888889\ \text{mph}

How to work it out

1
Write down what you know: distance d = 80 miles, time t = 9 hours. You are asked for the speed v.
2
Use the formula speed = distance ÷ time:
$v = \frac{d}{t} = \frac{80}{9} = \frac{80}{9} = 8.8888889$
3
Answer with the unit: 8.8888889 mph.
4
The same formula rearranged: distance = speed × time (8.8888889 × 9 = 80 miles) and time = distance ÷ speed (80 ÷ 8.8888889 = 9 hours).

LaTeX source of the formulas on this page

\[ v = \frac{d}{t} = \frac{80}{9} = 8.8888889\ \text{mph} \]
\[ v = \frac{d}{t} = \frac{80}{9} = \frac{80}{9} = 8.8888889 \]

What is the speed if a car travels 80 miles in 9 hours?

The average speed is 8.8888889 mph.

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

26.666667 miles.