What will come in place of the question mark (?) in the following numbers ?
15 12 17 10 ? 8 25 6

Options

A. 3
B. 17
C. 21
D. 19

Answer

To solve the problem, we need to identify the pattern in the sequence of numbers given:

15, 12, 17, 10, ?, 8, 25, 6.

Let's break down the sequence step by step:

1. **Identify the sequence**: We have the numbers: 15, 12, 17, 10, ?, 8, 25, 6.

2. **Look for patterns**: We can separate the numbers into two alternating sequences:
- First sequence: 15, 17, ?, 25
- Second sequence: 12, 10, 8, 6

3. **Analyze the first sequence**:
- The first sequence is: 15, 17, ?, 25.
- The difference between 15 and 17 is +2.
- The difference between 17 and 25 is +8.
- This suggests that the sequence is increasing by 2, then we need to find the missing number.

4. **Analyze the second sequence**:
- The second sequence is: 12, 10, 8, 6.
- The difference between 12 and 10 is -2.
- The difference between 10 and 8 is -2.
- The difference between 8 and 6 is -2.
- This suggests that the sequence is decreasing by 2 each time.

5. **Finding the missing number**:
- Following the pattern in the first sequence, if we add 2 to 17, we get 19.
- Thus, the missing number (?) is 19.

So, the complete sequence is: 15, 12, 17, 10, 19, 8, 25, 6.

The answer is: **19**.