Free Letter, Symbol and Number Series MCQs with Answers

1. Complete the series: 2, 6, 12, 20, 30, ?

• A. 36
• B. 40
• C. 42
• D. 46

Explanation: The differences between consecutive terms are 4, 6, 8, 10 — increasing by 2 each time. The next difference is 12, so the missing term is 30 + 12 = 42.

2. Find the next number in the series: 3, 6, 12, 24, ?

• A. 30
• B. 36
• C. 48
• D. 60

Explanation: Each term is double the one before it, so the next term is 24 times 2, which is 48. Checking a series for a constant ratio before looking for a constant difference saves time, since a rapidly growing series is almost always multiplicative. The answer 30 comes from assuming a difference of 6.

3. Find the next number in the series: 2, 5, 10, 17, 26, ?

• A. 35
• B. 37
• C. 39
• D. 41

Explanation: The differences are 3, 5, 7 and 9, rising by 2 each time, so the next difference is 11 and the next term is 26 plus 11, which is 37. The same series can be read as n squared plus 1 for n equal to 1, 2, 3 and so on, which gives 36 plus 1 for the sixth term. When first differences are not constant, always take the second differences.

4. Complete the letter series: A, C, F, J, ?

• A. M
• B. N
• C. O
• D. P

Explanation: The gaps between the letters grow by one each step: A to C skips one letter, C to F skips two, F to J skips three, so the next step skips four and lands on O. Writing the alphabet with position numbers turns this into the numeric series 1, 3, 6, 10, 15, which is the triangular numbers. The answer M comes from assuming a constant gap of three.

5. What will come next? 1, 4, 2, 5, 3, 6, 4, 7, ?

• A. 5
• B. 6
• C. 7
• D. 8

Explanation: Two sequences are interleaved: the terms in the odd positions run 1, 2, 3, 4 and those in the even positions run 4, 5, 6, 7, each rising by one. The next term sits in an odd position, so it continues the first sequence after 4, giving 5. Splitting an irregular looking series into alternate terms is the standard first move.

6. The virus spreads rapidly in the town. It infected the people - First day: 8, Second day: 16, Third day: 32. What will be the number of people infected on the next day?

• A. 44 people
• B. 56 people
• C. 64 people
• D. 74 people

Explanation: Each figure is double the one before, so the growth is geometric rather than arithmetic and the next term is 32 multiplied by 2, giving 64. Looking for a constant difference instead would suggest adding 16 to reach 48, which fits none of the options. Checking whether a series grows by a fixed amount or a fixed factor is always the first step.