A car travels 100 km in 9 hours. What is its average speed?

The average speed is 11.111111 km/h.

v = \frac{d}{t} = \frac{100}{9} = 11.111111\ \text{km/h}

How to work it out

1
Write down what you know: distance d = 100 km, time t = 9 hours. You are asked for the speed v.
2
Use the formula speed = distance ÷ time:
$v = \frac{d}{t} = \frac{100}{9} = \frac{100}{9} = 11.111111$
3
Answer with the unit: 11.111111 km/h.
4
The same formula rearranged: distance = speed × time (11.111111 × 9 = 100 km) and time = distance ÷ speed (100 ÷ 11.111111 = 9 hours).

LaTeX source of the formulas on this page

\[ v = \frac{d}{t} = \frac{100}{9} = 11.111111\ \text{km/h} \]
\[ v = \frac{d}{t} = \frac{100}{9} = \frac{100}{9} = 11.111111 \]

What is the speed if a car travels 100 km in 9 hours?

The average speed is 11.111111 km/h.

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

33.333333 km.