dr. chung's SAT math question!

Test Preparation
1

<p>hello everyone</p>

<p>on practice test 1, section 7, question 13 found on page 112 i don’t understand how chung got the answer.
the question says:</p>

<p>In the figure above, ABCD is a rectangle and line BM is perpendicular to line AC. If the length of AM is 2 and the length of CM is 18, what is the area of triangle ABC?</p>

<p>the answer is 60 and explanation says:
from the similar triangles, BM^2 = AM x MC so x^2 = 2(18) = 36
thus, x = 6
therefore, the area of triangle abc = 20(6) / 2 = 60</p>

2

<p>Triangles AMB and BMC are similar, so AM/BM = BM/MC. Rearranging gives BM^2 = AM*MC.</p>

<p>You know AM and MC so solving for BM is easy.</p>

<p>Then the area of the triangle is (1/2)AC*BM = (1/2)(20)(6) = 60.</p>