The number `144` can be represented by `12xx12` square grid . Which of the following can also be represented on a square grid ?

Options

A. `39`
B. `50`
C. `70`
D. `81`

Answer

To determine which of the given numbers can be represented on a square grid similar to how 144 is represented (as 12 x 12), we need to find out if each number can be expressed as a product of two equal integers (i.e., a perfect square).

### Step-by-Step Solution:

1. **Understand the concept of square grids**: A square grid can represent a number if that number can be expressed as the product of two equal integers (n x n), which means it is a perfect square.

2. **Identify the number 144**: The number 144 can be expressed as 12 x 12, which means it is a perfect square (12^2).

3. **Evaluate the options**:
- **Option 1: 39**
- Check if 39 is a perfect square:
- The square root of 39 is approximately 6.24, which is not an integer.
- Therefore, 39 cannot be represented on a square grid.

- **Option 2: 50**
- Check if 50 is a perfect square:
- The square root of 50 is approximately 7.07, which is not an integer.
- Therefore, 50 cannot be represented on a square grid.

- **Option 3: 70**
- Check if 70 is a perfect square:
- The square root of 70 is approximately 8.37, which is not an integer.
- Therefore, 70 cannot be represented on a square grid.

- **Option 4: 81**
- Check if 81 is a perfect square:
- The square root of 81 is 9, which is an integer.
- Therefore, 81 can be represented on a square grid as 9 x 9.

4. **Conclusion**: Among the options provided, only 81 can be represented on a square grid.

### Final Answer:
The number that can also be represented on a square grid is **81**.