In each of these questions a number series is given. In each series only one…
2024
In each of these questions a number series is given. In each series only one number is wrong. Find out the wrong number.
18225, 6075, 2025, 675, 220, 75, 25
Answer: C. 220 — ConceptIn a 'find the wrong number' series, first identify the single rule that links each term to the next (a constant ratio, a constant difference, or a…
- A.
25
- B.
75
- C.
220
- D.
18225
- E.
6075
Attempted by 23 students.
Show answer & explanation
Correct answer: C
Concept
In a 'find the wrong number' series, first identify the single rule that links each term to the next (a constant ratio, a constant difference, or a fixed operation). Once the rule is fixed, the one term that violates it is the wrong number.
Application
Test the ratio between consecutive terms from the left:
18225 ÷ 3 = 6075 — holds
6075 ÷ 3 = 2025 — holds
2025 ÷ 3 = 675 — holds
675 ÷ 3 = 225, but the series shows 220 — breaks the rule
225 ÷ 3 = 75 — holds
75 ÷ 3 = 25 — holds
The governing rule is 'divide the previous term by 3.' Every step obeys it except the fifth term, where the value should be 225 but appears as 220.
Cross-check
Replace 220 with 225 and read the corrected series: 18225, 6075, 2025, 675, 225, 75, 25. Now 225 ÷ 3 = 75 and 75 ÷ 3 = 25, so every consecutive pair has the exact ratio 3. This confirms 220 is the only term that does not fit, so 220 is the wrong number.