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
The lesson
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.
You can also add your own parentheses to an expression to change its answer. Try a few positions and check each one until you hit the number you want.
Solve the innermost brackets first, work outward, and the rest of the expression follows in order.
Watch it
Where it sits
This opens up
8 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.