A car travels 390 km in 5 hours. What is its average speed?

The average speed is 78 km/h.

v = \frac{d}{t} = \frac{390}{5} = 78\ \text{km/h}

How to work it out

1
Write down what you know: distance d = 390 km, time t = 5 hours. You are asked for the speed v.
2
Use the formula speed = distance ÷ time:
$v = \frac{d}{t} = \frac{390}{5} = 78$
3
Answer with the unit: 78 km/h.
4
The same formula rearranged: distance = speed × time (78 × 5 = 390 km) and time = distance ÷ speed (390 ÷ 78 = 5 hours).

LaTeX source of the formulas on this page

\[ v = \frac{d}{t} = \frac{390}{5} = 78\ \text{km/h} \]
\[ v = \frac{d}{t} = \frac{390}{5} = 78 \]

What is the speed if a car travels 390 km in 5 hours?

The average speed is 78 km/h.

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

234 km.