What will come in place of question mark(?) in the following number series?
19 ,39, 79 ,159 ,? ,639

Options

A. 321
B. 319
C. 280
D. 320

Answer

To find the missing number in the series 19, 39, 79, 159, ?, 639, we will analyze the pattern in the series step by step.

### Step 1: Identify the pattern
Let's look at the numbers in the series:
- 19
- 39
- 79
- 159
- ?
- 639

### Step 2: Find the relationship between consecutive terms
We will check how each number relates to the next one:
1. From 19 to 39:
- \( 19 \times 2 - 1 = 39 \)
2. From 39 to 79:
- \( 39 \times 2 + 1 = 79 \)
3. From 79 to 159:
- \( 79 \times 2 + 1 = 159 \)

### Step 3: Continue the pattern
Now, we will apply the same pattern to find the next term:
- From 159 to the missing term (?):
- \( 159 \times 2 + 1 = 319 \)

### Step 4: Verify the next term
Now, let's check the next term after the missing term:
- From 319 to 639:
- \( 319 \times 2 - 1 = 639 \)

### Conclusion
Thus, the missing number in the series is **319**.

### Final Answer
The number that comes in place of the question mark (?) is **319**.

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