What will come in the place of question mark (?) in the following number sereis:
`1800," "?," "60," "15," "5," "2.5`

Options

A. A)300
B. B)600
C. C)120
D. D)240

Answer

To solve the number series: `1800, "?", 60, 15, 5, 2.5`, we need to identify the pattern in the series.

### Step-by-Step Solution:

1. **Identify the Known Terms**:
The series is:
- First term: 1800
- Second term: ?
- Third term: 60
- Fourth term: 15
- Fifth term: 5
- Sixth term: 2.5

2. **Analyze the Pattern**:
To find the missing term, we can analyze the relationship between the known terms. We will work backwards from the last known term (2.5) to the first term (1800).

3. **Calculate the Ratios**:
- From 2.5 to 5:
- \( 5 = 2.5 \times 2 \)
- From 5 to 15:
- \( 15 = 5 \times 3 \)
- From 15 to 60:
- \( 60 = 15 \times 4 \)

We can see that each term is multiplied by an increasing integer:
- The multiplier from 2.5 to 5 is 2.
- The multiplier from 5 to 15 is 3.
- The multiplier from 15 to 60 is 4.

4. **Continue the Pattern**:
Following this pattern, we can deduce:
- From 60 to the second term (?), we should multiply by 5.
- From the second term (?) to 1800, we should multiply by 6.

5. **Calculate the Missing Term**:
- To find the second term (?), we can either:
- Multiply 60 by 5:
\[ ? = 60 \times 5 = 300 \]
- Or divide 1800 by 6:
\[ ? = \frac{1800}{6} = 300 \]

6. **Conclusion**:
Therefore, the missing term in the series is **300**.

### Final Answer:
The missing term is **300**.