Question:

In the number series 4, 10, 23, 50, 104, 216, 439 the wrong number is

Show Hint

Try doubling and adding a growing number: 4 times 2 plus 2 gives 10, 10 times 2 plus 3 gives 23, 23 times 2 plus 4 gives 50. Carry on and see which printed term does not match.
Updated On: Jul 17, 2026
  • 10
  • 23
  • 104
  • 50
Show Solution
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The Correct Option is C

Solution and Explanation

Step 1: Look for the rule linking one term to the next.
The terms grow roughly twofold each time, so the likely rule is "double and add something". Test that on the first pair.
\[ 4 \times 2 + 2 = 10 \]
So the first step is double and add 2.

Step 2: Check the next few steps to see if the added number follows its own pattern.
\[ 10 \times 2 + 3 = 23 \]
\[ 23 \times 2 + 4 = 50 \]
So far the added numbers are 2, 3, 4, rising by one each time. The rule looks like: double the previous term and add 2, then 3, then 4, then 5, and so on.

Step 3: Apply the rule to the next term.
After 50, the number to be added should be 5:
\[ 50 \times 2 + 5 = 105 \]
But the series prints 104, not 105. That is the first place the rule breaks.

Step 4: Confirm by checking the remaining terms.
If the correct term is 105, the next added number should be 6:
\[ 105 \times 2 + 6 = 216 \]
The series shows 216, so it matches.
Then the added number should be 7:
\[ 216 \times 2 + 7 = 439 \]
The series shows 439, which matches too.
So every term after the suspect one fits the rule perfectly, provided the fifth term is taken as 105. This proves the single wrong entry is 104.

Step 5: Check that 216 and 439 do not work from 104.
Starting from the printed 104, the rule would give \( 104 \times 2 + 6 = 214 \), not 216. So keeping 104 would break two later terms instead of one. A well-formed series question has exactly one wrong term, so 104 must be the odd one out.

Step 6: Clear the other options.
Option (A) 10 fits \( 4 \times 2 + 2 \). Correct.
Option (B) 23 fits \( 10 \times 2 + 3 \). Correct.
Option (D) 50 fits \( 23 \times 2 + 4 \). Correct.
Only 104 fails, and it should be 105.

Final Answer:
The wrong number in the series is 104, which should be 105.
\[ \boxed{104} \]
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