Question

which exspression results in a rational number ?
1.
$\sqrt{121 } - \sqrt{21}$
2.
$\sqrt{25} \times \sqrt{50}$
3.
$\sqrt{36} \div \sqrt{225}$
4.
$3 \sqrt{5} + 2 \sqrt{5}$
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Answer 1

3) since root(36)=6 and root(225)=15 so 6 divided by 15 is 2/5 (0.4) which is a rational number