Question

In each of the questions below, one term in the given number series is wrong. Find out the wrong term.
11, 5, 20, 12, 40, 26, 74, 54

• A. 5
• B. 20
• C. 40
• D. 26

Hint:

Split the series into alternate (odd-position and even-position) sub-series and check each one for a pattern.

Answer 1

The Correct Option is C

Step 1: Split the series into two alternating sub-series.
Series: 11, 5, 20, 12, 40, 26, 74, 54.
Odd-position terms (1st, 3rd, 5th, 7th): 11, 20, 40, 74.
Even-position terms (2nd, 4th, 6th, 8th): 5, 12, 26, 54.

Step 2: Check the even-position sub-series.
5 to 12 is +7.
12 to 26 is +14.
26 to 54 is +28.
The additions double each time (7, 14, 28), so this sub-series is completely consistent, with no error.

Step 3: Check the odd-position sub-series.
11 to 20 is +9.
20 to 40 is +20, but if the same doubling pattern (9, 18, 36) held, the next addition should have been +18, giving 20 + 18 = 38, not 40.
Checking forward, 38 to 74 is +36, which fits the doubling pattern (9, 18, 36) perfectly.
So the 5th term of the overall series, shown as 40, should actually be 38.

Final Answer:
The wrong term in the series is 40. \[ \boxed{40} \]