SAT square root question

[Math Tutor]

[tex]\sqrt{20}-\sqrt{5}=[/tex]

Answers:
(A) $\sqrt{15}$
(B) $\sqrt{10}$
(C) $\sqrt{5}$
(D) $\sqrt{2.5}$

[red12dog34]

[tex]\displaystyle\sqrt{20}=\sqrt{2^2\cdot 5}=2\sqrt{5}[/tex]
[tex]\sqrt{20}-\sqrt{5}=2\sqrt{5}-\sqrt{5}=\sqrt{5}[/tex]
The answer is (C).

[mycalsuite]

√20 - √5=?
√20= √4.5= 2√5
√20 - √5= 2√5 - √5 = (2-1)√5 = √5

The correct answer is C √5.

[nycmath]

So, sqrt{20} = sqrt{4} • sqrt{5}.

sqrt{4} = 2

2•sqrt{5} - sqrt{5}

(2 - 1)(sqrt{5}) = sqrt{5}

Answer = C