A car travels 390 miles in 5 hours. What is its average speed?
The average speed is 78 mph.
How to work it out
- 1
Write down what you know: distance d = 390 miles, time t = 5 hours. You are asked for the speed v.
- 2
Use the formula speed = distance ÷ time:
- 3
Answer with the unit: 78 mph.
- 4
The same formula rearranged: distance = speed × time (78 × 5 = 390 miles) and time = distance ÷ speed (390 ÷ 78 = 5 hours).
LaTeX source of the formulas on this page
\[ v = \frac{d}{t} = \frac{390}{5} = 78\ \text{mph} \]
\[ v = \frac{d}{t} = \frac{390}{5} = 78 \]How far at 78 mph
| Time | Distance |
|---|---|
| 0.5 hours | 39 miles |
| 1 hour | 78 miles |
| 2 hours | 156 miles |
| 3 hours | 234 miles |
| 4 hours | 312 miles |
| 5 hours | 390 miles |
Questions
What is the speed if a car travels 390 miles in 5 hours?
The average speed is 78 mph.
How far does it go in 3 hours at that speed?
234 miles.