Grade 3 · Unit 4: Patterns and algebra

Number patterns and rules

Find the rule, extend the pattern.

Growing plants

A seedling is 2 cm tall and grows 3 cm a week. 2, 5, 8, 11, 14 … This is a sequence with the rule “add 3”.

Extending sequences

Find the difference between terms. 14 − 7 = 7, 21 − 14 = 7. The rule is add 7. Next: 35, 42.

Function machines

An input goes in, the rule acts, an output comes out. 3 → 12, 5 → 20. So 8 → 32.

Two-step rules

Some rules have two steps. 1 → 3, 2 → 5, 3 → 7: multiply by 2, then add 1. What will 10 become? 21.

Patterns in place value

Look down and across the table. What do you notice? Multiplying by 20 is like multiplying by 2, then by 10. Patterns in place value help us calculate quickly. Show a pattern as a table, a drawing or a graph – choose what fits best.

The core, in a new form

In 1, 3, 4, 1, 3, 4 … the core is 1, 3, 4. Show the same pattern with beads: 1 red, 3 blue, 4 green, again and again. Shrinking patterns go down: 18, 15, 12, 9, 6 – the rule is take away 3.

What I learnt

• I can find and extend number sequences.
• I can use function machines.
• I can describe two-step rules.