Missing Number

Missing number questions hide a rule linking numbers in a group. Test simple operations on the complete groups, then apply the rule to the incomplete one.

🎯 Try it yourself

Tap an answer. You'll see if it's right, and why. Easy ones come first.

1. Q1Easy

   Find the missing number: (8, 9, 17), (10, 4, 14), (5, 3, ?)

   1. A34
   2. B8
   3. C7
   4. D16
   Show answer

   Answer: B. 8

   💡 In each group the third number is a + b, so 5 + 3 = 8.

2. Q2Easy

   Find the missing number: (11, 9, 99), (5, 5, 25), (5, 2, ?)

   1. A10
   2. B7
   3. C3
   4. D21
   Show answer

   Answer: A. 10

   💡 In each group the third number is a × b, so 5 × 2 = 10.

3. Q3Easy

   Find the missing number: (10, 3, 13), (7, 10, 17), (7, 5, ?)

   1. A35
   2. B24
   3. C12
   4. D74
   Show answer

   Answer: C. 12

   💡 In each group the third number is a + b, so 7 + 5 = 12.

4. Q4Medium

   Find the missing number: (2, 2, 6), (7, 5, 54), (5, 7, ?)

   1. A32
   2. B74
   3. C12
   4. D35
   Show answer

   Answer: A. 32

   💡 In each group the third number is a² + b, so 5² + 7 = 32.

5. Q5Medium

   Find the missing number: (12, 7, 38), (6, 8, 28), (8, 7, ?)

   1. A20
   2. B30
   3. C71
   4. D15
   Show answer

   Answer: B. 30

   💡 In each group the third number is (a + b) × 2, so (8 + 7) × 2 = 30.

6. Q6Medium

   Find the missing number: (2, 4, 12), (5, 6, 22), (10, 9, ?)

   1. A181
   2. B38
   3. C91
   4. D71
   Show answer

   Answer: B. 38

   💡 In each group the third number is (a + b) × 2, so (10 + 9) × 2 = 38.

7. Q7Hard

   Find the missing number: (5, 11, 146), (9, 8, 145), (6, 7, ?)

   1. A105
   2. B91
   3. C93
   4. D85
   Show answer

   Answer: D. 85

   💡 In each group the third number is a² + b², so 6² + 7² = 85.

8. Q8Hard

   Find the missing number: (7, 6, 13), (5, 3, 16), (10, 5, ?)

   1. A125
   2. B75
   3. C82
   4. D105
   Show answer

   Answer: B. 75

   💡 In each group the third number is a² − b², so 10² − 5² = 75.