Take-Away Tricks: Subtracting Without Counting on Fingers
You have 9 crayons. Your little brother grabs 3 of them. How many are left? You could count 9 fingers, fold down 3, and count what's left one by one. Or you could use a trick that gets you the answer almost instantly. Today you learn two of those tricks!
What You'll Learn
- How to subtract by counting UP instead of counting down - How to use doubles you already know to subtract fast - How to use a number line to jump backward - How to check a subtraction answer using addition
Trick 1: Count Up Instead of Down
For 9 - 3, instead of counting backward from 9, count UP from 3 to 9: 3...4...5...6...7...8...9. That's 6 jumps. So 9 - 3 = 6. This trick works best when the two numbers are close together, like 8 - 6. Counting up from 6 to 8 is just 2 jumps (7, 8), so 8 - 6 = 2. Counting down from 8 would take longer!
Trick 2: Use Doubles You Already Know
If you know that 5 + 5 = 10, you also know 10 - 5 = 5 for free! Doubles facts like 6+6=12, 7+7=14, and 8+8=16 all hide a subtraction fact inside them. So if a problem says 14 - 7, and you remember 7 + 7 = 14, you instantly know the answer is 7. No counting needed at all — just remembering one fact unlocks two.
Trick 3: Jump Backward on a Number Line
Draw a line with numbers 0 to 10 on it. For 8 - 3, put your finger on 8, then hop backward 3 times: land on 7, then 6, then 5. You land on 5, so 8 - 3 = 5. The number line trick is great for bigger jumps because you can also jump in chunks — hop back 2, then back 1 more — instead of one number at a time.
Every subtraction fact has an addition fact hiding inside it! If 6 - 2 = 4, then 4 + 2 = 6 is also true. You can always check a subtraction answer by adding the answer back to the smaller number — if you get the starting number back, you got it right.
You want to solve 9 - 7 using the counting up trick. What do you count?
You know that 8 + 8 = 16. Which subtraction fact does this instantly tell you?
Flashcards — click each card to reveal the answer
Crayon Box Subtraction Hunt
Get 10 small objects (crayons, buttons, or blocks). Line them all up. Have a partner secretly take away some and hide them behind their back. Count how many are left in the line, then figure out how many your partner is hiding using the counting-up trick. Do this 5 times and write down each subtraction sentence, like '10 - 4 = 6.' Circle any problem where you used a doubles fact to solve it faster.
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