• We can use formulas to model real-life situations.

• For example, the formula for calculating speed is speed = distance ÷ time.

• It is possible to calculate the speed, distance or time if you have the other two values.

What is speed?

Speed tells us how fast something or someone is travelling. You can find the average speed of an object if you know the distance travelled and the time it took.

The formula for speed is speed = distance ÷ time. To work out what the units are for speed, you need to know the units for distance and time. In this example, distance is in metres (m) and time is in seconds (s), so the units will be in metres per second (m/s).

Rearranging the formula

The formula speed = distance ÷ time can be rearranged, just like any other equation.

The formula can be rearranged in three ways:

• speed = distance ÷ time

• distance = speed × time

• time = distance ÷ speed

To calculate one of the variables (speed, distance or time) we need the other two.

For example, to find the time taken to make a journey, we need the length of the journey and the speed of travel.

Formula quiz

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