algebra · Year 4 · AC9M4N09
Function machines
A function machine takes a number in, does something to it, and sends a new number out. This one has a two-step rule: first multiply, then add. To find the output, put the input through both steps in order. For In 8 with the rule × 2 + 1: first 8 × 2 = 16, then 16 + 1 = 17, so Out is 17. Always do the steps in the order the machine shows them, and remember to do BOTH — the multiply and the add.
Sample questions
In 8 → Out 19, In 5 → Out 13. Rule: × 2 + 3. What comes out for In 1?
- The rule is × 2 then + 3.
- 1 × 2 = 2.
- 2 + 3 = 5.
Answer: 5
In 5 → Out 15, In 1 → Out 7. Rule: × 2 + 5. What comes out for In 6?
- The rule is × 2 then + 5.
- 6 × 2 = 12.
- 12 + 5 = 17.
Answer: 17
In 9 → Out 23, In 5 → Out 15. Rule: × 2 + 5. What comes out for In 2?
- The rule is × 2 then + 5.
- 2 × 2 = 4.
- 4 + 5 = 9.
Answer: 9