Typical speed-distance-time questions on numeracy tests ask you to work out one of the three quantities, given the other two. You can see that speed is related to distance and time if you just think about the units you use for it: you typically give a speed in miles per hour (or in kilometres per hour).

In fact, the units give you a clue as to the formula: if you translate ‘per’ as ‘divide by’, it tells you that the speed (in miles per hour) is the distance (in miles) divided by the time taken (in hours). Put another way, speed = distance ÷ time.

You might find it a bit easier to remember the equation with a formula triangle like the one shown.

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The three types of question are:

  • Find the speed, given the distance and time. Looking at the formula triangle, you can work out that the speed is the distance divided by the time.

  • Find the distance, given the speed and the time. Again, if you look at the formula triangle, you can see that you get distance by multiplying speed by time.

  • Find the time, given the speed and the distance. The formula triangle says that you get the time by dividing distance by speed.

Sometimes, an exam tries to trip you up by giving a time in minutes rather than hours. Always make sure you convert times into hours before you try to do any sums in miles per hour or kilometres per hour. And remember an hour has 60 minutes, not 100!

Finding the speed

Here are the steps for finding the speed if you know the distance and time:

  1. Draw the SDT triangle.

  2. Cover up the thing you’re trying to find (the S for Speed).

  3. Read off the sum you need to do: D ÷ T, or distance divided by time. (The D is above the T, so you divide.)

  4. Write down the sum with the numbers you’re given for distance and time, and work out the answer!

Finding the distance

Here are the steps for finding the distance if you know the speed and time:

  1. Draw the SDT triangle.

  2. Cover up the thing you’re trying to find (the D for Distance).

  3. Read off the sum you need to do: S x T, or speed times time. (The S and T are on the same level, so it’s a multiplication.)

  4. Write down the sum with the numbers you’re given for speed and time, and work out the answer!

Finding the time

Getting familiar? Here are the steps for finding the time if you know the distance and speed:

  1. Draw the SDT triangle.

  2. Cover up the thing you’re trying to find (the T for Time).

  3. Read off the sum you need to do: D ÷ S, or distance divided by speed.

  4. Write down the sum with the numbers you’re given for distance and speed, and work out the answer!