Two-step: Finding the rule in function machines (worked example)
22 October 2026
When your child meets a function machine with two steps, it can seem tricky at first. Breaking each part down helps them see exactly what is happening to the number as it moves through the machine.
Worked example
A function machine has two steps. First, multiply the input by 3. Then add 4. If the input is 5, what is the output?
5 × 3 = 15
15 + 4 = 19
The correct answer is 19.
Now your child can spot the rule in a two-step function machine. They know to follow each step in order, so they can work out the answer. This type of question is common in 11+ maths, and practising similar problems will help them feel more confident.
