In each of the following questions, a series of number / alphabet is given which follow certain rules. One of the number / alphabet is missing. Choose the missing number / alphabets from the alternatives given below and mark it on your answer - sheet as directed.
18, 24, 21, 27, ?, 30, 27,

Options

A. 33
B. 30
C. 24
D. 21

Answer

To solve the series: 18, 24, 21, 27, ?, 30, 27, we need to identify the pattern in the sequence.

### Step 1: Identify the pattern
Let's analyze the series step by step:

1. Start with the first number: **18**
2. The second number is **24**. This is obtained by adding **6** to **18**:
\[ 18 + 6 = 24 \]

3. The third number is **21**. This is obtained by subtracting **3** from **24**:
\[ 24 - 3 = 21 \]

4. The fourth number is **27**. This is obtained by adding **6** to **21**:
\[ 21 + 6 = 27 \]

5. Now, we need to find the missing number (let's call it **x**). According to the pattern, the next operation should be subtracting **3** from **27**:
\[ 27 - 3 = 24 \]
So, **x = 24**.

6. The sixth number is **30**, which is obtained by adding **6** to **24**:
\[ 24 + 6 = 30 \]

7. Finally, the last number is **27**, which is obtained by subtracting **3** from **30**:
\[ 30 - 3 = 27 \]

### Conclusion
The missing number in the series is **24**.

### Final Answer
**24**