37
Subtracting a sum from a number
Textbook: Part 1, lesson 36, pp. 76–77
GoalLearn subtracting a sum from a number: a − (b + c).
New words
subtracting a sum from a number · sondan yig‘indini ayirishminuend · kamayuvchidisc · diskremaining · qolgan
Explanation
To subtract a sum from a number we can subtract the addends one after the other: a − (b + c) = (a − b) − c = (a − c) − b. Or we first find the sum and then subtract it. Both ways give the same result.
Worked examples
20 − (5 + 7) = 20 − 12 = 8; or (20 − 5) − 7 = 15 − 7 = 8.
97 − (12 + 27) = (97 − 12) − 27 = 85 − 27 = 58.
Class activity
“Storekeeper”: from 50 objects children take away one group and then another. They calculate how many are left and check by counting.
Practice
1
36 − (16 + 11) = ?
9
2
58 − (29 + 8) = ?
21
3
97 − (12 + 27) = ?
58
4
A class has 30 pupils. 8 do sport, 11 do music and the rest draw. How many pupils draw?
11