Brackets in Expressions
Use parentheses, brackets, or braces in numerical expressions and evaluate expressions containing these grouping symbols
What a learner can do afterwards
- Evaluate 3 × (4 + 5) by computing inside the parentheses first
- Evaluate {2 × [3 + (7 − 1)]} with nested grouping symbols
- Insert parentheses into an expression to make it equal a target value
1 · Read
Some math problems use brackets like parentheses ( ), square brackets [ ], or braces { } around part of an expression. These brackets are a signal: solve what is inside them before you do anything else.
Look at 3 × (4 + 5). The parentheses tell you to add first: 4 + 5 = 9. Now the expression is 3 × 9. Multiply to get 27.
Now look at {2 × [3 + (7 − 1)]}. Start with the deepest brackets: 7 − 1 = 6. Next, work outward: 3 + 6 = 9. Last, multiply: 2 × 9 = 18.
After the brackets, multiply and divide before you add and subtract. Then work from left to right. So 1 + 2 × 5 is 1 + 10 = 11. Brackets can change that order: (1 + 2) × 5 is 3 × 5 = 15. To hit a target number, try brackets in different places and check each one.
Solve the innermost brackets first, work outward, and the rest of the expression follows in order.
Readings 'Brackets come first', 'Brackets inside brackets' and 'Placing brackets to hit a target' are original to this dataset. All 10 extra questions are original to this dataset.
2 · Watch
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Where it sits
18 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.