受 · Subtraction
Scroll of the Block
Subtraction is the distance between two numbers. Pick the direction that makes the distance easiest to see.
Step Back
When you take away a small number, just step backwards along the number line.
12 − 3
- → Start at 12
- → Step back: 11, 10, 9
Answer: 9
Practice: Try 15 − 2, 21 − 3 and 40 − 4.
Close the Gap
When the numbers are close together, count up from the smaller one. Stop at round numbers on the way.
100 − 73
- → 73 + 7 = 80
- → 80 + 20 = 100
- → Gap: 7 + 20 = 27
Answer: 27
Also great for change: 43 − 39 → 39 to 40 is 1, 40 to 43 is 3, so the gap is 4.
Practice: Try 61 − 58, 100 − 46 and 1000 − 875.
Through the Gate
Split the number you subtract so you land exactly on ten first, then take away the rest.
14 − 6
- → 14 − 4 = 10 (land on the gate)
- → 6 − 4 leaves 2
- → 10 − 2 = 8
Answer: 8
Bigger numbers work the same way: 52 − 18 = 52 − 10 − 8 = 34.
Practice: Try 13 − 5, 32 − 7 and 71 − 26.
Into the dojo
Practise with the Block − technique in Kung Fu Math or Junior, white belt and up.