50
Brackets
Textbook Part 2, pp. 20–21
GoalUnderstand that brackets show which operation is done first.
New words
brackets ( ) · qavs ( )order of operations · amallar tartibileft to right · chapdan o‘ngga
Explanation
In an expression without brackets, operations are done left to right: 7 − 3 + 10 = 4 + 10 = 14. To show which operation comes first, we put it in brackets: 3 + (5 + 5) = 3 + 10 = 13.
Worked examples
A zoo cage had 5 partridges and 4 pheasants; 10 quails were added: (5 + 4) + 10 = 9 + 10 = 19.
A store had 7 sacks of grain; 3 were taken out and 10 brought in: 7 − 3 + 10 = 14 sacks.
Class activity
Hand brackets: the teacher writes an expression; a child “wraps” the part done first with both hands and works it out.
Practice
1
4 + (6 + 3) = ?
13
2
(9 − 4) + 7 = ?
12
3
10 − 5 + 6 = ?
11
4
12 − (5 + 5) = ?
2