33
Column subtraction
Textbook: Part 1, lesson 32, pp. 68–69
GoalLearn column subtraction of two-digit numbers with regrouping.
New words
column · ustunborrowing · qarz olishminuend · kamayuvchisubtrahend · ayriluvchi
Explanation
We write ones under ones and tens under tens. If the ones of the minuend are smaller than the ones of the subtrahend, we borrow one ten and add 10 to the ones. Then we subtract the tens, remembering that one ten was lent.
Worked examples
82 − 47: 2 is too small, so 12 − 7 = 5. Tens: 8 − 1 = 7, 7 − 4 = 3. Answer 35.
41 − 29: 11 − 9 = 2; 4 − 1 = 3, 3 − 2 = 1. Answer 12.
Class activity
“Borrow dot”: when a ten is borrowed we put a small dot above it. Children solve 5 sums and count the dots.
Practice
1
37 − 19 = ?
18
2
52 − 28 = ?
24
3
84 − 57 = ?
27
4
46 patients were booked to see the doctor. 18 have been seen. How many are still waiting?
28