73
Multi-step expressions with brackets
Textbook Part 2, pp. 66–67
GoalWork out multi-step expressions with and without brackets in the right order.
New words
rule · qoidapredator · yirtqich hayvonto breathe · nafas olmoq
Explanation
If an expression has brackets, do the bracket first, then the rest left to right. Without brackets — left to right. 50 − (20 + 10) = 50 − 30 = 20, but 50 − 20 + 10 = 40. Brackets can change the answer!
Worked examples
A zoo has 2 tigers, 5 lions and 8 leopards: (2 + 5) + 8 = 15 big cats.
A person breathes about 20 times a minute and a pigeon 30 times: 30 − 20 = 10 times more.
Class activity
“Where do the brackets go?” — the board shows 20 − 5 + 3. Children place brackets in two ways and see the answers differ (18 and 12).
Practice
1
50 − (20 + 10) = ?
20
2
50 − 20 + 10 = ?
40
3
(12 + 11) + 6 = ?
29
4
80 − (45 − 15) = ?
50