What will come in place of the question mark(?) in the following number series
9 11 15 23 39 ?

Options

A. 71
B. 61
C. 75
D. 76

Answer

To solve the number series: 9, 11, 15, 23, 39, ?, we will analyze the differences between consecutive terms and identify a pattern.

### Step-by-step Solution:

1. **Identify the series**: The given series is 9, 11, 15, 23, 39, ?.

2. **Calculate the differences between consecutive terms**:
- Difference between 11 and 9:
\[ 11 - 9 = 2 \]
- Difference between 15 and 11:
\[ 15 - 11 = 4 \]
- Difference between 23 and 15:
\[ 23 - 15 = 8 \]
- Difference between 39 and 23:
\[ 39 - 23 = 16 \]

So, the differences are: 2, 4, 8, 16.

3. **Observe the pattern in the differences**:
- The differences are: 2, 4, 8, 16.
- Each difference is double the previous one:
- \(2 \times 2 = 4\)
- \(4 \times 2 = 8\)
- \(8 \times 2 = 16\)

4. **Find the next difference**:
- Following the pattern, the next difference should be:
\[ 16 \times 2 = 32 \]

5. **Add the next difference to the last term of the series**:
- The last term in the series is 39. We add the next difference (32):
\[ 39 + 32 = 71 \]

6. **Conclusion**:
- The number that comes in place of the question mark (?) is 71.

### Final Answer:
The answer is 71.