What should come in place of question mark (?) in the following…
2025
What should come in place of question mark (?) in the following number/alphabetic series?
Complete the series 162, 54, 18, 6, ? by replacing the question mark ‘?’.
- A.
2
- B.
3
- C.
4
- D.
5
Show answer & explanation
Correct answer: A
Concept: For a series based on a constant ratio (a Geometric Progression), each term is obtained by multiplying -- or dividing -- the previous term by a fixed common ratio r. To find a missing term, first identify r from the given terms, then apply the same operation to the last known term.
Application:
Check the ratio between consecutive given terms: 54 ÷ 162 = 1/3, 18 ÷ 54 = 1/3, 6 ÷ 18 = 1/3. The common ratio r = 1/3.
Apply the same ratio to the last given term to find the next one: 6 × 1/3 = 2.
Cross-check: Multiplying back up the series with ratio 3 recovers the original terms -- 2 × 3 = 6, 6 × 3 = 18, 18 × 3 = 54, 54 × 3 = 162 -- confirming consistency.
So the missing term is 2.