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Function machines practice questions with answers

Foundation · Grade 2 · Non-calculator

A second set of function machines questions for GCSE Maths. They are different from the ones on the topic page, so work through both. Try each question, then open the answer to check your working.

More questions

Question 1 Easy

A function machine does × 2 then − 5. The output is 9. What is the input?

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Answer: 7

  1. Undo the last step first: 9 + 5 = 14.
  2. Then undo the multiplication: 14 ÷ 2 = 7.
  • Method (1): Undo the last step first: 9 + 5 = 14.
  • Accuracy (1): Answer 7

Question 2 Easy

A function machine does × 3 then + 4. The input is 8. What is the output?

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Answer: 28

  1. × 3 first: 8 × 3 = 24.
  2. Then + 4: 24 + 4 = 28.
  • Method (1): × 3 first: 8 × 3 = 24.
  • Accuracy (1): Answer 28

Question 3 Medium

A function machine does × 3 then + 4. The input is 11. What is the output?

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Answer: 37

  1. × 3 first: 11 × 3 = 33.
  2. Then + 4: 33 + 4 = 37.
  • Method (1): × 3 first: 11 × 3 = 33.
  • Accuracy (1): Answer 37

Question 4 Medium

A function machine does × 2 then − 5. The input is 12. What is the output?

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Answer: 19

  1. × 2 first: 12 × 2 = 24.
  2. Then − 5: 24 − 5 = 19.
  • Method (1): × 2 first: 12 × 2 = 24.
  • Accuracy (1): Answer 19

Question 5 Hard

A function machine does × 2 then − 5. The input is 15. What is the output?

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Answer: 25

  1. × 2 first: 15 × 2 = 30.
  2. Then − 5: 30 − 5 = 25.
  • Method (1): × 2 first: 15 × 2 = 30.
  • Accuracy (1): Answer 25

Question 6 Hard

A function machine does × 3 then + 4. The output is 52. What is the input?

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Answer: 16

  1. Undo the last step first: 52 − 4 = 48.
  2. Then undo the multiplication: 48 ÷ 3 = 16.
  • Method (1): Undo the last step first: 52 − 4 = 48.
  • Accuracy (1): Answer 16

Exam-style question

A longer question with marks, in the style of a written paper. This is a Yumio practice question, not a past paper question.

Exam-style question 12 marks

A function machine does × 2 then − 5. The input is 18. What is the output?

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Answer: 31

  1. × 2 first: 18 × 2 = 36.
  2. Then − 5: 36 − 5 = 31.
  3. The output is 31.
  • Method (1): × 2 first: 18 × 2 = 36.
  • Accuracy (1): Answer 31

Quick checks

Short one-step questions. Pick an option before you open the answer.

Check 1

A function machine does × 3 then + 4. The output is 70. What is the input?

  1. 22
  2. 24
  3. 32
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22 The result is 22.

Check 2

A function machine does × 3 then + 4. The input is 23. What is the output?

  1. 73
  2. 75
  3. 83
Show answer

73 The result is 73.

Check 3

A function machine does × 2 then − 5. The input is 24. What is the output?

  1. 43
  2. 45
  3. 53
Show answer

43 The result is 43.

Check 4

A function machine does × 2 then − 5. The output is 45. What is the input?

  1. 25
  2. 27
  3. 35
Show answer

25 The result is 25.

Check 5

A function machine does × 3 then + 4. The input is 26. What is the output?

  1. 82
  2. 84
  3. 92
Show answer

82 The result is 82.

Check 6

A function machine does × 2 then − 5. The input is 27. What is the output?

  1. 49
  2. 51
  3. 59
Show answer

49 The result is 49.

Check 7

A function machine does × 3 then + 4. The output is 88. What is the input?

  1. 28
  2. 30
  3. 38
Show answer

28 The result is 28.

Check 8

A function machine does × 3 then + 4. The input is 29. What is the output?

  1. 91
  2. 93
  3. 101
Show answer

91 The result is 91.

Check 9

A function machine does × 2 then − 5. The input is 30. What is the output?

  1. 55
  2. 57
  3. 65
Show answer

55 The result is 55.

Check 10

A function machine does × 2 then − 5. The output is 57. What is the input?

  1. 31
  2. 33
  3. 41
Show answer

31 The result is 31.

Check 11

A function machine does × 3 then + 4. The input is 32. What is the output?

  1. 100
  2. 102
  3. 110
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100 The result is 100.

Check 12

A function machine does × 2 then − 5. The input is 33. What is the output?

  1. 61
  2. 63
  3. 71
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61 The result is 61.

Check 13

A function machine does × 3 then + 4. The output is 106. What is the input?

  1. 34
  2. 36
  3. 44
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34 The result is 34.

Check 14

A function machine does × 3 then + 4. The input is 35. What is the output?

  1. 109
  2. 111
  3. 119
Show answer

109 The result is 109.

Check 15

A function machine does × 2 then − 5. The input is 36. What is the output?

  1. 67
  2. 69
  3. 77
Show answer

67 The result is 67.

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