Consider the following pattern of numbers : 8 | 10 | 15 | 13 6 | 5 | 7 | 4 4 | 6 | 8 | 8 —————— 6 | 11 | 16 | ? What is the number at ? in the above pattern?
- (a) 17 ✓ UPSC's answer
- (b) 19
- (c) 21
- (d) 23
Why the answer is (a)
• Observe the first column: 8 + 6 + 4 = 18, which is not 6; however, 8 - 6 + 4 = 6, matching the bottom row.
• Check the second column: 10 - 5 + 6 = 11, which matches the bottom row value.
• Verify the third column: 15 - 7 + 8 = 16, which matches the bottom row value.
• The pattern for each column is: (Top Number) - (Middle Number) + (Bottom Number) = (Result Number).
• Apply this pattern to the fourth column: 13 - 4 + 8 = 17.
• Therefore, the missing number is 17, which corresponds to option (a).
Why the other options are wrong
- (b) 19
- 19 is incorrect because 13 - 4 + 8 equals 17, not 19.
- (c) 21
- 21 is incorrect because the calculation 13 - 4 + 8 yields 17, not 21.
- (d) 23
- 23 is incorrect because the calculation 13 - 4 + 8 yields 17, not 23.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2018, held on 3 June 2018. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.