Given right triangle ABCABC with altitude \overline{BD}BD drawn to hypotenuse ACAC. If AC=20AC=20 and DC=5,DC=5, what is the length of \overline{BC}?BC? (Note: the figure is not drawn to scale.)
AC - DC = AD
20 - 5 = 15
AD / BD = BD / CD
15 / BD = BD / 5
15 * 5 = BD^2
75 = BD^2
AC^2 = BD^2 + CD^2
AC^2 = 75 + 5^2
AC^2 = 75 + 25
AC^2 =100
AC = 10