Here is a quick one to do in your head: what is 62 − 58?

When you have an answer, think about how you got it. Did you take 58 away from 62, step by step? Or did you start at 58 and count up to 62? Both can work, but one of them is much faster here.

Four subtractions, one at a time: 53 − 8, 71 − 68, 84 − 30 and 93 − 88.

Say each one aloud before the arcs appear, then decide: do we count back, or count up? Look at how far apart the two numbers are before you choose.

Now we work four subtractions together on the one number line: 45 − 7, 66 − 62, 79 − 40 and 83 − 78.

For each one, a pupil comes up and does three things: decide whether the two numbers are far apart or close together, tap the start number and type the number the jumps will start from, then add the jumps. Counting back starts on the bigger number. Counting up starts on the smaller one. Far apart means count back. Close together means count up. The rest of the class agrees or corrects out loud before we move on.

When you count back, the number you land on is the answer. When you count up, the answer is how far you jumped, not the number you land on: for 66 − 62 you start at 62 and jump 4 up to 66, so the answer is 4. Read the jumps, not the Total box.

Now you work these four on your own, one at a time: 56 − 9, 52 − 48, 84 − 30 and 93 − 88.

For each one, decide the strategy before you touch anything. Far apart means count back. Close together means count up. Then add the jumps and press Check. Counting back, the number you land on is the answer. Counting up, the answer is how far you jumped.

Today we learned

• Subtraction can be done two ways: take away (count back) or find the difference (count up).
• Close numbers are quicker to count up; far-apart numbers are quicker to count back.
• Jump arcs let us see each step of the strategy on the number line.

Coming up

Next we move on to writing addition out in columns, where we regroup across the place-value columns.