Why does my kid's subtraction look so different?
Borrowing is now called regrouping, and kids learn it with blocks and number lines before the shortcut. Here is what they are doing and how to help.
Your 2nd grader brings home 52 − 17. You reach for the method you know: cross out the 5, make it a 4, put a little 1 next to the 2. Your kid looks at you like you have three heads. Their teacher showed them something else. The good news: it is the same math.
"Borrowing" is now "regrouping"
When you borrowed, you were really breaking one ten into ten ones. Schools now teach that step with real objects first, so kids understand why it works before they learn the shortcut.
Try it below. Start with 52 (5 tens and 2 ones). You need to take away 7 ones, but there are only 2. Tap Break a ten into 10 ones and watch what happens.
Tens
Ones
5 tens, 2 ones = 52
52 = 50 + 2
Another way: count up on a number line
Many classrooms also teach subtraction as finding the distance between two numbers. Start at 17 and jump to 52 in friendly hops: +3 to 20, +30 to 50, +2 to 52. Add the jumps: 3 + 30 + 2 = 35.
Start at 17
Tap a button, or tap any spot on the line to jump there.
How to help without confusing them
- Ask "how did your teacher show you?" before showing your way.
- Use real things: bundle 10 straws with a rubber band to make a "ten".
- Your method is fine too, later. Once they understand regrouping, the shortcut makes sense.
