23
Subtracting (33 − 7)
Textbook: Part 1, lesson 22, pp. 48–49
GoalLearn subtracting by breaking a ten when the ones are too few (33 − 7).
New words
subtracting with regrouping · xonadan o‘tib ayirishbreaking a ten · o‘nlikni ochishelectronic · elektronto check · tekshirish
Explanation
We cannot take 7 from 3 ones. We change 1 ten into 10 ones: 3 tens 3 ones = 2 tens 13 ones. 13 − 7 = 6, so the answer is 2 tens 6 ones = 26.
Worked examples
42 − 6: 4 tens 2 ones = 3 tens 12 ones; 12 − 6 = 6, so the answer is 36.
51 − 3 = 4 tens 11 ones − 3 ones = 48.
Class activity
“Borrowing from the bank”: when there are too few ones, children take one ten from the “tens bank” and swap it for 10 ones. They show each sum with cubes.
Practice
1
65 − 8 = ?
57
2
34 − 6 = ?
28
3
51 − 3 = ?
48
4
The class has 32 pupils. 6 were absent today. How many pupils came?
26