A car travels 20 km in 8 hours. What is its average speed?

The average speed is 2.5 km/h.

v = \frac{d}{t} = \frac{20}{8} = 2.5\ \text{km/h}

How to work it out

1
Write down what you know: distance d = 20 km, time t = 8 hours. You are asked for the speed v.
2
Use the formula speed = distance ÷ time:
$v = \frac{d}{t} = \frac{20}{8} = \frac{5}{2} = 2.5$
3
Answer with the unit: 2.5 km/h.
4
The same formula rearranged: distance = speed × time (2.5 × 8 = 20 km) and time = distance ÷ speed (20 ÷ 2.5 = 8 hours).

LaTeX source of the formulas on this page

\[ v = \frac{d}{t} = \frac{20}{8} = 2.5\ \text{km/h} \]
\[ v = \frac{d}{t} = \frac{20}{8} = \frac{5}{2} = 2.5 \]

What is the speed if a car travels 20 km in 8 hours?

The average speed is 2.5 km/h.

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

7.5 km.