In each of the following number series only one Is wrong . Find out the wrong number in the given number series
4 5.1 7.3 10.6 15 20 27.1

Options

A. 5.1
B. 4
C. 7.3
D. 20

Answer

To find the wrong number in the given series: 4, 5.1, 7.3, 10.6, 15, 20, 27.1, we will analyze the differences between the consecutive numbers.

### Step-by-step Solution:

1. **Identify the series**: The series given is:
\[ 4, 5.1, 7.3, 10.6, 15, 20, 27.1 \]

2. **Calculate the differences between consecutive terms**:
- Difference between 5.1 and 4:
\[ 5.1 - 4 = 1.1 \]
- Difference between 7.3 and 5.1:
\[ 7.3 - 5.1 = 2.2 \]
- Difference between 10.6 and 7.3:
\[ 10.6 - 7.3 = 3.3 \]
- Difference between 15 and 10.6:
\[ 15 - 10.6 = 4.4 \]
- Difference between 20 and 15:
\[ 20 - 15 = 5 \]
- Difference between 27.1 and 20:
\[ 27.1 - 20 = 7.1 \]

3. **List the differences**:
- The differences are:
\[ 1.1, 2.2, 3.3, 4.4, 5, 7.1 \]

4. **Identify the pattern in the differences**:
- The differences appear to follow a pattern where each difference increases by 1.1:
- \(1.1\) (which is \(1.1 \times 1\))
- \(2.2\) (which is \(1.1 \times 2\))
- \(3.3\) (which is \(1.1 \times 3\))
- \(4.4\) (which is \(1.1 \times 4\))
- \(5.5\) (which should be \(1.1 \times 5\))
- \(6.6\) (which should be \(1.1 \times 6\))

5. **Determine the expected difference**:
- Following the pattern, the difference after 15 should be \(5.5\), leading to:
\[ 15 + 5.5 = 20.5 \]
- However, the next number in the series is 20, which is incorrect.

6. **Conclusion**:
- The wrong number in the series is **20**. The correct number should be **20.5**.

### Final Answer:
The wrong number in the series is **20**.