Function or Number Machines is a maths skill that is commonly tested in 11+ exams and UK selective tests.
Examples
Example Question 1:
54 → [÷ 9] → __
Answer: 6
Explanation: Apply the rule [÷ 9] so 54 ÷ 9 = 6
Example Question 2:
36 → [÷ 3] → [+ 20] → __
Answer: 32
Explanation: Apply the two rules in the order given [÷ 3] = 12, then [+ 20] = 32
Example Question 3:
__ ← [– 9] ← 57
Answer: 66
Explanation: Do the inverse of the rule to find the beginning number 57 + 9 = 66
Example Question 4:
25 → [ ? ] → 7 find the rule
Answer: –18
Explanation: Find the rule by doing an inverse operation 25 – 7 = 18
Video for a two-stage number machine:
Video for how to find the rule:
