2, 31, 247, 987, 1973, 1971, 985

Options

A. 1971
B. 987
C. 31
D. 985

Explanation

To find the odd one out in the series: 2, 31, 247, 987, 1973, 1971, 985, we will analyze the pattern of the numbers step by step.

### Step 1: Identify the pattern
The series starts with small numbers and then increases significantly before decreasing. We will look for a multiplication pattern.

### Step 2: Analyze the first two numbers
From 2 to 31:
- We can see that \(2 \times 16 - 1 = 31\).

### Step 3: Analyze the next pair
From 31 to 247:
- We can see that \(31 \times 8 - 1 = 247\).

### Step 4: Analyze the next pair
From 247 to 987:
- We can see that \(247 \times 4 - 1 = 987\).

### Step 5: Analyze the next number
From 987 to 1973:
- We need to determine the multiplication factor. If we assume a similar pattern, we can try \(987 \times 2 - 1\).
- However, \(987 \times 2 = 1974\), so \(1974 - 1 = 1973\) fits the pattern.

### Step 6: Check the next number
From 1973 to 1971:
- Here, we see a decrease instead of an expected increase. This suggests that 1971 might be the odd one out.

### Step 7: Verify the next number
From 1971 to 985:
- If we follow the pattern, we would expect \(1972 \times 0.5 - 1\) to lead to 985.
- \(1972 \times 0.5 = 986\), and \(986 - 1 = 985\).

### Conclusion
The number 1971 does not fit the established pattern, as the expected number should be 1972 instead. Therefore, the odd one out in the series is **1971**.

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