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Find the missing number in the series: 7 : 56 :: 9 : ?
72
81
90
99
90
Identify the relationship as n(n + 1). For 7, it is 7 * (7 + 1) = 56. For 9, it is 9 * (9 + 1) = 90.
Identify the relationship as n(n + 1). For 7, it is 7 * (7 + 1) = 56. For 9, it is 9 * (9 + 1) = 90.
Analyze the relationship between 7 and 56
The number 56 can be expressed as 7 multiplied by 8. In terms of the original number n=7, this is n * (n + 1), which is 7 * 8 = 56.
Apply the same logic to the number 9
Using the identified pattern n * (n + 1), where n = 9, we calculate 9 * (9 + 1) = 9 * 10 = 90.
A: 72 is incorrect as it results from 8 * 9, not following the n(n+1) pattern. B: 81 is incorrect as it is simply 9 squared. D: 99 is incorrect as it is 9 * 11, missing the consecutive integer requirement.
C is correct because the pattern follows n(n+1); for n=7, 78=56, and for n=9, 910=90.
In number analogies, always check if the second number is a square, a cube, or a product of consecutive integers; these are the most frequent patterns in RRB and SSC exams.
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