Step-by-step rules | Year 3

01 / LEARN

The idea, step by step

A step-by-step rule tells you what to do first, next and last. Read all the instructions before starting, then carry them out in order.

“Add 3, then double” is not the same as “double, then add 3”. Try both rules with the same starting number to see why.

If a rule says double and add 1, both actions belong to one round. Record the answer after both actions are finished.

Keep the starting number separate from the results. Each new result becomes the next starting number.

Start at 2. Each round: double, then add 1.
Round	Start	Double	Add 1: result
1	2	4	5
2	5	10	11
3	11	22	23

Swap the instructions because the same operations appear.

Instead: Changing the order can change the answer. Follow the order given.

02 / WORKED EXAMPLES

Example 1

Start at 4. Add 3, then double.

14.

Example 2

Start at 1. Each round, add 2 then double. Find the first 2 results.

6, then 16.

Start at 5. Double, then subtract 1.

Show answer

$5 + 5 = 10$ , then $10 - 1 = 9$ .

03 / WORKSHEET

6 questions · Work at your own pace.

Read the questions online

Read the worked solutions

Start at 3. Add 4, then subtract 2.
$3 + 4 = 7$ ; $7 - 2 = 5$ .
5.
Start at 6. Double, then add 3.
$6 + 6 = 12$ ; $12 + 3 = 15$ .
15.
Start at 6. Add 3, then double. Compare with the previous answer.
$6 + 3 = 9$ ; $9 + 9 = 18$ .
18; it is 3 more than 15.
Start at 10. Subtract 2 each round. Give the first 3 results.
$10 - 2 = 8$ ; $8 - 2 = 6$ ; $6 - 2 = 4$ .
8, 6, 4.
Start at 2. Each round, double then add 1. Find the second result.
Round 1 gives $2 + 2 + 1 = 5$ . Round 2 gives $5 + 5 + 1 = 11$ .
11.
Change 7 into 15 using add 1 and double, each once. Give the order.
$7 + 7 = 14$ ; $14 + 1 = 15$ . Adding 1 first would give 16.
Double, then add 1.

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Decisions in number rules

Curriculum reference & lesson scope

Australian Curriculum v9 and SA Curriculum Mathematics

Number sequences; step-by-step rules; decisions; explaining resulting patterns.