Which of the following is not a perfect square?

Options

A. 361
B. 1156
C. 1128
D. 1681

Answer

To determine which of the given options is not a perfect square, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Options**: We have four numbers to consider: 361, 1156, 1681, and 1128.

2. **Check 361**:
- Calculate the square root of 361.
- \( \sqrt{361} = 19 \)
- Since 19 is an integer, 361 is a perfect square.

3. **Check 1156**:
- Calculate the square root of 1156.
- \( \sqrt{1156} = 34 \)
- Since 34 is an integer, 1156 is a perfect square.

4. **Check 1681**:
- Calculate the square root of 1681.
- \( \sqrt{1681} = 41 \)
- Since 41 is an integer, 1681 is a perfect square.

5. **Check 1128**:
- Calculate the square root of 1128.
- \( \sqrt{1128} \approx 33.6 \) (not an integer)
- Since the square root is not an integer, 1128 is not a perfect square.

### Conclusion:
The number that is not a perfect square is **1128**.

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