In each of the following questions one number is missing to understand the pattern of the series and then insert the missing number .
17,24,19,22,?,20,23,18,25

Options

A. 23
B. 21
C. 12
D. 20

Answer

To find the missing number in the series 17, 24, 19, 22, ?, 20, 23, 18, 25, we can analyze the pattern of the numbers.

1. **Identify the two alternating sequences**:
- The first sequence consists of the numbers at the odd positions: 17, 19, ?, 23, 25.
- The second sequence consists of the numbers at the even positions: 24, 22, 20, 18.

2. **Analyze the second sequence (even positions)**:
- The sequence is: 24, 22, 20, 18.
- We can see that each number is decreasing by 2:
- 24 - 2 = 22
- 22 - 2 = 20
- 20 - 2 = 18
- This confirms that the pattern is consistent.

3. **Analyze the first sequence (odd positions)**:
- The sequence is: 17, 19, ?, 23, 25.
- Here, we can see:
- 17 + 2 = 19
- To find the missing number, we can look at the next number:
- 19 + 2 = ?
- Therefore, ? = 21.

4. **Confirm the pattern with the next number**:
- Continuing the pattern:
- 21 + 2 = 23 (which is the next number in the sequence).
- This confirms that our missing number is indeed 21.

5. **Final answer**:
- The missing number in the series is 21.