51
Brackets: order of operations
Textbook Part 2, pp. 22–23
GoalFollow the order of operations in expressions with several brackets; write a bracketed expression for a problem.
New words
first of all · birinchi navbatdathen · keyinexpression · ifoda
Explanation
The order: 1) first the operations inside brackets; 2) if there are several brackets, do them left to right; 3) then the remaining operations left to right. Example: (3 + 7) + (2 + 4) = 10 + 6 = 16.
Worked examples
First 3 adults and 7 children entered the zoo, then 2 adults and 4 children: (3 + 7) + (2 + 4) = 16 people.
The same problem: (3 + 2) + (7 + 4) = 5 + 11 = 16 — another way, same answer.
Class activity
Two teams write two different bracketed expressions for the same problem and check that the answers match.
Practice
1
(4 + 6) + (5 + 3) = ?
18
2
(8 + 2) − (3 + 4) = ?
3
3
15 − (2 + 3) + 4 = ?
14
4
A feed bag has 4 apples, 3 carrots and 5 bananas. Write an expression and work it out.
(4 + 3) + 5 = 12