To find which measure could be the actual length of the diagonal of the square, we will calculate the approximate values of the given lengths:
- \( \sqrt{50} \approx 7.07 \)
- \( \sqrt{40} \approx 6.32 \)
- \( \sqrt{13} \approx 3.61 \)
- \( \sqrt{21} \approx 4.58 \)
The problem states that the length of the diagonal is 7 inches when rounded to the nearest whole number. Thus, the actual length of the diagonal must be between 6.5 inches and 7.5 inches.
Now, we compare the calculated values to this range:
- \( \sqrt{50} \approx 7.07 \) (within the range)
- \( \sqrt{40} \approx 6.32 \) (not within the range)
- \( \sqrt{13} \approx 3.61 \) (not within the range)
- \( \sqrt{21} \approx 4.58 \) (not within the range)
The only value that fits the criteria, being within the range of 6.5 to 7.5 inches, is:
\( \sqrt{50} \).