What will come in place of the question mark (?) in the following number series?
`120" "15" "105" "17.5" "87.5" "?`

Options

A. 18.5
B. 19.5
C. 21.875
D. 17.5

Answer

To find the missing term in the series `120, 15, 105, 17.5, 87.5, ?`, we will analyze the pattern of the series step by step.

### Step 1: Identify the pattern
The series alternates between division and multiplication. Let's break it down:

1. **From 120 to 15**:
- We divide 120 by 8.
- \( 120 \div 8 = 15 \)

2. **From 15 to 105**:
- We multiply 15 by 7.
- \( 15 \times 7 = 105 \)

3. **From 105 to 17.5**:
- We divide 105 by 6.
- \( 105 \div 6 = 17.5 \)

4. **From 17.5 to 87.5**:
- We multiply 17.5 by 5.
- \( 17.5 \times 5 = 87.5 \)

### Step 2: Continuing the pattern
Now, we need to find the next term after 87.5. Following the established pattern, the next operation should be a division.

5. **From 87.5 to ?**:
- We will divide 87.5 by 4 (since the pattern of divisors is decreasing: 8, 7, 6, 5, and now 4).
- \( 87.5 \div 4 = 21.875 \)

### Conclusion
Thus, the missing term in the series is **21.875**.

### Summary of Steps:
1. Identify the operation between each pair of terms.
2. Recognize the pattern of alternating multiplication and division.
3. Apply the next operation (division by 4) to find the missing term.