Question

Which of the following is a rational number: 32−−√
32
, 81−−√
81
, 90−−√
90
, or 125−−−√
125

Answer 1

To determine which of the numbers is a rational number, we need to check whether each of the square roots is a whole number (an integer) since square roots that are whole numbers are rational.

1. \( \sqrt{32} \approx 5.656 \) (not a rational number)
2. \( \sqrt{81} = 9 \) (a rational number)
3. \( \sqrt{90} \approx 9.487 \) (not a rational number)
4. \( \sqrt{125} \approx 11.180 \) (not a rational number)

Among the numbers given, \( \sqrt{81} \) is a rational number because it equals 9, which is an integer.

Therefore, the answer is \( \sqrt{81} \).