Which one of the following is not correct ?

Options

A. `sqrt(0.4096) = 0.64`
B. `sqrt(40.96) = 6.4`
C. `sqrt(0.04096) = 0.064`
D. `sqrt(4096) = 64`

Answer

To determine which of the given options is not correct, we need to evaluate each option by squaring the numbers on the left-hand side and comparing them to the right-hand side.

### Step-by-Step Solution:

1. **Evaluate the first option:**
- Left-hand side: \(0.64\)
- Right-hand side: \(0.64^2\)
- Calculation: \(0.64^2 = 0.64 \times 0.64 = 0.4096\)
- Conclusion: Left-hand side equals right-hand side. This option is correct.

2. **Evaluate the second option:**
- Left-hand side: \(6.4\)
- Right-hand side: \(6.4^2\)
- Calculation: \(6.4^2 = 6.4 \times 6.4 = 40.96\)
- Conclusion: Left-hand side equals right-hand side. This option is correct.

3. **Evaluate the third option:**
- Left-hand side: \(0.064\)
- Right-hand side: \(0.064^2\)
- Calculation: \(0.064^2 = 0.064 \times 0.064 = 0.004096\)
- Conclusion: Left-hand side \(0.064\) does not equal right-hand side \(0.004096\). This option is not correct.

4. **Evaluate the fourth option:**
- Left-hand side: \(64\)
- Right-hand side: \(64^2\)
- Calculation: \(64^2 = 64 \times 64 = 4096\)
- Conclusion: Left-hand side equals right-hand side. This option is correct.

### Final Conclusion:
The option that is not correct is the third option.