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P.1 Addition and subtraction sentences - up to 20

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What are mixed operations?

Mixed operations are math problems that use both addition and subtraction in the same set of exercises. These problems help you practice when to add and when to subtract.

Examples:
  • 5 + 3 = 8
  • 9 - 4 = 5
  • 7 + 2 - 3 = 6
Note

Mixed operations problems may include both addition and subtraction, but the answers will stay within 20.

How do you identify addition and subtraction?

Addition problems use the plus sign (+) to show putting numbers together. Subtraction problems use the minus sign (-) to show taking numbers away.

Examples:
  • 4 + 6 = 10 (plus sign means add)
  • 12 - 7 = 5 (minus sign means subtract)
  • 8 + 5 - 3 = 10 (first add, then subtract)
Note

Always look carefully at the operation signs to decide whether to add or subtract.

Steps for solving mixed operations

To solve mixed operations, work from left to right unless parentheses are used. Solve one step at a time.

Steps:
  • Look at the first two numbers and the operation.
  • Solve that part of the problem.
  • Use your answer to solve the next part.
Note

Do not skip steps. Solve in order from left to right to get the correct answer.

Practice with sentences

Word problems help you see how addition and subtraction work in real life.

Examples:
  • Tom has 7 apples. He buys 5 more. Now he has 12 apples. (7 + 5 = 12)
  • Sara has 10 balloons. She gives 3 away. She has 7 left. (10 - 3 = 7)
  • Mike has 8 marbles. He wins 4 more, then loses 2. Now he has 10. (8 + 4 - 2 = 10)
Note

Underline the important numbers in word problems to help decide if you should add or subtract.