Paper 1 · Mathematical Reasoning and Aptitude
Find the missing number in the following series: 3, 4, 7, 7, 13, 13, 21, 22, 31, 34, ?
A41
B43 ✓ Correct
C45
D47
Correct answer: (B) 43 — The missing number is 43, so that is the answer.
Explanation
★The missing number is 43, so that is the answer.
★The series interleaves two separate patterns in alternate positions.
★The odd-position terms are 3, 7, 13, 21, 31, ?, with differences 4, 6, 8, 10.
★The missing term is the eleventh, which is an odd position.
★So the next difference is 12, giving 31 plus 12.
★This gives 43.
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