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3.08 Writing expressions using order of operations

Lesson

Are you ready?

Stories can help us to understand the operations that need to happen, in order to solve a problem. Have a look at this story, to remember how to write a number sentence to represent the story.  

Ursula collected sticks at the park and laid them on the ground in $2$2 groups with $2$2 sticks in each group.

John also collected sticks and laid them on the ground in $5$5 groups with $3$3 sticks in each group.

Ursula:                    
                   
John:                       
  1. Which number sentence matches the total number of sticks?

    $2+2\times5+3$2+2×5+3

    A

    $2+2+5+3$2+2+5+3

    B

    $2\times2+5\times3$2×2+5×3

    C


Learn

This video shows us how the order of operations is used in everyday problems.

Apply

Question 1

Write the number sentence described as:

Multiply $2$2 less than $7$7 with $2$2 less than $9$9.

Question 2

At a self-serve checkout, a couple is sorting their groceries into plastic-free bags. They have a total of $77$77 items and place $7$7 items aside to carry on their own. The remaining $70$70 items are evenly separated into their bags, with $14$14 items in each bag.

  1. Which number sentence describes the amount of bags and items they have to carry?

    $70\div14+7$70÷​14+7

    A

    $70\times14+7$70×14+7

    B

    $70+14\div7$70+14÷​7

    C

    $70+14\times7$70+14×7

    D

 

Remember!

The order of operations:

  1. Solve anything inside grouping symbols (brackets).
  2. Solve any multiplication or division, including powers, working from left to right.
  3. Solve any addition or subtraction, working from left to right.

Outcomes

5.OA.A.2

Write simple expressions that record calculations with numbers, and interpret numerical expressions without evaluating them (e.G., Express the calculation "add 8 and 7, then multiply by 2" as 2 x (8 + 7). Recognize that 3 x (18,932 + 921) is three times as large as 18,932 + 921, without having to calculate the indicated sum or product).

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