What will come in place of the question mark (?) in the following number series.
10 12 18 30 50 ?

Options

A. 88
B. 78
C. 80
D. 74

Answer

To solve the number series problem: 10, 12, 18, 30, 50, ?, we will analyze the differences between the consecutive numbers in the series.

### Step-by-Step Solution:

1. **Identify the series**: The given series is 10, 12, 18, 30, 50, ?.

2. **Calculate the differences between consecutive terms**:
- Difference between 12 and 10:
\[ 12 - 10 = 2 \]
- Difference between 18 and 12:
\[ 18 - 12 = 6 \]
- Difference between 30 and 18:
\[ 30 - 18 = 12 \]
- Difference between 50 and 30:
\[ 50 - 30 = 20 \]

So, the differences are: 2, 6, 12, 20.

3. **Calculate the differences of the differences**:
- Difference between 6 and 2:
\[ 6 - 2 = 4 \]
- Difference between 12 and 6:
\[ 12 - 6 = 6 \]
- Difference between 20 and 12:
\[ 20 - 12 = 8 \]

So, the second level of differences is: 4, 6, 8.

4. **Identify the pattern in the second level of differences**:
- The second level of differences is increasing by 2 each time (4, 6, 8).

5. **Predict the next difference in the second level**:
- The next difference after 8 would be:
\[ 8 + 2 = 10 \]

6. **Calculate the next difference in the first level**:
- Add this new difference (10) to the last difference (20):
\[ 20 + 10 = 30 \]

7. **Find the next term in the original series**:
- Add this new difference (30) to the last term in the original series (50):
\[ 50 + 30 = 80 \]

Thus, the number that will come in place of the question mark (?) is **80**.

### Final Answer:
The answer is **80**.