What is the value of the expression $3 \sqrt{80} - \sqrt{20}$

Correct answer marked below

4 \sqrt{5}

5 \sqrt{3}

10 \sqrt{5}

Correct

12 \sqrt{3}

20 \sqrt{5}

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Comments

KamranAug 5

I got 10√5 but can someone explain why we can't just subtract 20 from 80 under one big radical? that's where I messed up at first

SaranchanaAug 10

because the roots have to match before you can combine them, you simplify each one separately first

AsadJul 20

wait how does 3√80 turn into something with √5? I keep getting stuck there

LilianaJul 24

break 80 into 16 times 5, then the 16 comes out as 4

DrewJul 27

oh that makes way more sense, ty

What this question tests

Your handling of square and higher roots, including simplifying radicals.

Forgetting the ± when taking a square root to solve an equation, or assuming √(a²) = a.