Exams › SSC CGL (Prelims) › General › Number Series and Coding-Decoding
3 questions with worked solutions.
Q1. If $5 + 3 = 16$ and $7 + 4 = 33$, then $6 + 2 = ?$
Answer: 32
The pattern is $a + b = a^2 - b$ or equivalently a custom operation based on the first number. For $5 + 3$, $5^2 - 9 = 16$ and for $7 + 4$, $7^2 - 16 = 33$; the intended pattern here is $a^2 - b^2$? But matching the given examples, the consistent rule is $a^2 - b^2 + b$? Using the standard SSC-style intended pattern, $6 + 2 = 36 - 4 = 32$.
Q2. What number will replace the question mark? $2, 6, 14, 30, ?, 126$
Answer: 62
The differences are $+4, +8, +16, +32, +64$. So the missing term is $30 + 32 = 62$, and then $62 + 64 = 126$ matches the last term. This is a doubling-difference series.
Q3. Complete the series: $3, 9, 27, ?, 243$
Answer: 81
This is a geometric series where each term is multiplied by 3. So $3, 9, 27, 81, 243$. The missing term is 81.