Find a wrong number in the series:
7, 28, 63, 124, 215, 342, 511.

Options

A. 7
B. 28
C. 124
D. 215

Explanation

To find the wrong number in the series: 7, 28, 63, 124, 215, 342, 511, we will analyze the pattern of the series step by step.

### Step 1: Identify the pattern
We need to check if the numbers in the series can be expressed in a specific mathematical form. Observing the numbers, we can see that they seem to relate to cubes of integers.

### Step 2: Check each number
1. **7**: This can be expressed as \(2^3 - 1 = 8 - 1 = 7\).
2. **28**: This should be \(3^3 - 1 = 27 - 1 = 26\). However, it is given as 28.
3. **63**: This can be expressed as \(4^3 - 1 = 64 - 1 = 63\).
4. **124**: This can be expressed as \(5^3 - 1 = 125 - 1 = 124\).
5. **215**: This can be expressed as \(6^3 - 1 = 216 - 1 = 215\).
6. **342**: This can be expressed as \(7^3 - 1 = 343 - 1 = 342\).
7. **511**: This can be expressed as \(8^3 - 1 = 512 - 1 = 511\).

### Step 3: Identify the wrong number
From our analysis, we see that all numbers fit the pattern of \(n^3 - 1\) except for **28**. Instead of \(28\), the correct number should be **26** (which is \(3^3 - 1\)).

### Conclusion
Thus, the wrong number in the series is **28**.

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