In the following number series only one is wrong. Find out the wrong number.
8, 11, 17, 47, 128, 371, 1100

Options

A. 11
B. 47
C. 17
D. 371

Answer

To find the wrong number in the series 8, 11, 17, 47, 128, 371, 1100, we will analyze the pattern in the sequence step by step.

### Step 1: Identify the pattern
Let's look at the first few numbers in the series:
- Start with 8.

### Step 2: Calculate the next number
To find the next number, we can try multiplying the previous number by 3 and then subtracting a constant.

1. For 8:
\[ 8 \times 3 - 13 = 24 - 13 = 11 \]
So, the next number is 11.

### Step 3: Continue the pattern
2. For 11:
\[ 11 \times 3 - 13 = 33 - 13 = 20 \]
However, the next number in the series is 17, not 20. This indicates that 17 might be the wrong number.

### Step 4: Check the next number
3. For 17:
\[ 17 \times 3 - 13 = 51 - 13 = 38 \]
But the next number in the series is 47.

### Step 5: Check the following numbers
4. For 47:
\[ 47 \times 3 - 13 = 141 - 13 = 128 \]
This is correct.

5. For 128:
\[ 128 \times 3 - 13 = 384 - 13 = 371 \]
This is also correct.

6. For 371:
\[ 371 \times 3 - 13 = 1113 - 13 = 1100 \]
This is correct as well.

### Conclusion
The sequence shows that instead of 17, the correct number should be 20. Therefore, the wrong number in the series is **17**.