# Distance, speed and time calculations

In this blog, we will look at distance, speed and time calculations and I will show you a handy trick that will help you to remember how to calculate them.

First of all – distance, speed and time are all related. If you have two of them, you can use them to find the other one. For example, if I know how long a journey took and the speed of the journey, I can work out the distance travelled. Or if I know how long the journey took and the distance travelled, I can work out the speed.

The three terms are related by the following three equations:

Speed = Distance ÷ Time
Distance = Speed × Time
Time = Distance ÷ Speed

But, instead of remembering those three equations, you can remember just this triangle.

In this triangle D stands for Distance, S for Speed and T for Time.

This is really useful because you can use this triangle to obtain any of the three equations above.

To use the triangle, simply put your hand over what you are trying to find and what you are left with is your equation.

For example, if I wanted to find distance, I would cover up the D, and would be left with S × T – see below. So we get Distance = Speed × Time.

If I wanted to find speed, I would cover up the S and be left with D ÷ T. So Speed = Distance ÷ Time.

If I wanted to find time, I would cover up the T and be left with D ÷ S. So Time = Distance ÷ Speed.

Let’s do some examples.

Example 1
Usain ran 200 metres in 20 seconds.
Work out Usain’s speed, in metres per second.

We are finding speed, so we will cover up the S.

So Speed = Distance ÷ Time

Speed = 200 ÷ 20 = 10 metres per second.

Example 2
A car travelled for 3 hours at an average speed of 40 miles per hour.
Work out the distance travelled by the car.

We are finding distance, so we will cover up the D.

Distance = Speed × Time

Distance = 40 × 3 = 120 miles.

Example 3
A cyclist cycled 42 miles at an average speed of 12 miles per hour.
Work out how many hours the cyclist cycled for.

We are finding time, so we cover up the T.

Time = Distance ÷ Speed

Time = 42 ÷ 12 = 3.5 hours.

So that’s a more efficient way for remembering the distance, speed and time formulas. It’s much easier to remember a triangle than it is to remember three formulas.

This same idea can also be used with density/mass/volume and pressure/force/area calculations.

This can also be used for trigonometry (SOHCAHTOA).

I hope you have found that useful – I always encourage my students to use these triangles.

If you would like to practice this method with some more distance/speed/time questions, try our worksheet.

If you need someone to explain this to you in person, book in a free taster session.

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