How do you simplify sqrt216?

1 Answer
Apr 30, 2016

sqrt(216) = 6sqrt(6)

Explanation:

The quick version is:

sqrt(216) = sqrt(6^2*6) = 6sqrt(6)

How do we find out that 216 = 6^2*6 ?

One way is to split off prime factors one at a time, then recombine them.

Here's a factor tree for 216:

color(white)(0000)216
color(white)(0000)"/"color(white)(0)"\"
color(white)(000)2color(white)(00)108
color(white)(000000)"/"color(white)(0)"\"
color(white)(00000)2color(white)(00)54
color(white)(0000000)"/"color(white)(00)"\"
color(white)(000000)2color(white)(000)27
color(white)(000000000)"/"color(white)(00)"\"
color(white)(00000000)3color(white)(0000)9
color(white)(000000000000)"/"color(white)(0)"\"
color(white)(00000000000)3color(white)(000)3

So we find:

216 = 2*2*2*3*3*3=(2*3*2*3)*(2*3) = 6^2*6

By definition:

sqrt(6^2) = 6

For any positive numbers a and b we have:

sqrt(ab) = sqrt(a)sqrt(b)

Hence:

sqrt(216) = sqrt(6^2*6) = sqrt(6^2)sqrt(6) = 6sqrt(6)