Subtracting with regrouping

In your book, Maths Mela (Chapter 7), the buses stop for a snack. 83 children buy pusaw and 46 children buy fruit plates. How many more children bought pusaw? We find 83 − 46. First estimate: about 80 − 50 = 30.

Start from the ones. We must take 6 ones from 3 ones, but 3 ones are not enough. So we regroup 1 ten as 10 ones. Now there are 7 tens and 13 ones. 13 ones − 6 ones = 7 ones. 7 tens − 4 tens = 3 tens. So 83 − 46 = 37. 37 more children bought pusaw.

Sometimes no regrouping is needed. 438 children go to see the Living Roots Bridge, and 215 go first. 438 − 215: ones 8 − 5 = 3, tens 3 − 1 = 2, hundreds 4 − 2 = 2. So 223 children are waiting.

Sometimes we regroup twice. Lou and Daisy brought ₹310 and have ₹179 left. They spent ₹310 − ₹179. There are 0 ones, so regroup 1 ten as 10 ones: 10 − 9 = 1. Now 0 tens are left, not enough to take 7, so regroup 1 hundred as 10 tens: 10 − 7 = 3. Hundreds: 2 − 1 = 1. They spent ₹131. Check by adding: 179 + 131 = 310.