57
Subtracting from ten
Textbook Part 2, pp. 34–35
GoalAnother method: take the number away from the ten, then add the ones (13 − 8 = (10 − 8) + 3).
New words
subtracting from the ten · o‘nlikdan ayirishice cube · muz bo‘lakchasimethod · usul
Explanation
13 − 8 can also be done another way: 13 = 10 + 3. Take 8 from the ten: 10 − 8 = 2. Then add the ones back: 2 + 3 = 5. Both methods give the same answer — choose the one that suits you.
Worked examples
A saucer had 11 ice cubes and 6 are left: 11 − 6 = 5 melted.
8 of 15 ice cubes went into juice: 15 − 8 = (10 − 8) + 5 = 7.
Class activity
In pairs: one child uses “subtract in parts” and the other “subtract from ten” on the same sum. They compare answers.
Practice
1
12 − 9 = ?
3
2
17 − 8 = ?
9
3
11 − 7 = ?
4
4
Find the pattern: 20, 18, 16, _, _
14, 12