Here is a subtraction from a hurling scoreboard: 53 − 48.

One way is to count back: start at 53 and take away forty-eight, jump by jump. Another way is to count up: start at 48 and see how far it is up to 53. Which way would you pick, and why?

We will look at four subtractions together, each solved with jumps. Notice how the jumps change: sometimes we hop back, sometimes it is quicker to jump up. Notice which strategy fits each pair of numbers.

While we work, everyone decides the route in your own head. Thumbs up if you agree with the answer on the board, thumbs sideways if you would change something.

After that we call out three more together: 80 − 20, then 63 − 58, then 71 − 67. For each one, say whether you would count back or count up before anyone answers.

Now you spot the smart route. We work through these one at a time: 38 − 6, then 70 − 30, then 61 − 58, then 95 − 88. The numbers get closer together as we go, so watch for the moment the gap is small enough that counting up wins.

What we learned today

• You can subtract by counting back to take away, or by counting up to find the gap.
• Both routes give the same answer — counting up is quicker when the two numbers are close together.
• Look at the numbers first to choose the smart route before you start jumping.

Coming up