A car travels 90 km in 7 hours. What is its average speed?

The average speed is 12.857143 km/h.

v = \frac{d}{t} = \frac{90}{7} = 12.857143\ \text{km/h}

How to work it out

1
Write down what you know: distance d = 90 km, time t = 7 hours. You are asked for the speed v.
2
Use the formula speed = distance ÷ time:
$v = \frac{d}{t} = \frac{90}{7} = \frac{90}{7} = 12.857143$
3
Answer with the unit: 12.857143 km/h.
4
The same formula rearranged: distance = speed × time (12.857143 × 7 = 90 km) and time = distance ÷ speed (90 ÷ 12.857143 = 7 hours).

LaTeX source of the formulas on this page

\[ v = \frac{d}{t} = \frac{90}{7} = 12.857143\ \text{km/h} \]
\[ v = \frac{d}{t} = \frac{90}{7} = \frac{90}{7} = 12.857143 \]

What is the speed if a car travels 90 km in 7 hours?

The average speed is 12.857143 km/h.

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

38.571429 km.