bigtreezl wrote:

scthakur wrote:

S1. Tells you that the two triangles ABC and KLM are similar traingles

A1/A2 = AB^2/KL^2

4/1 = AB^2/10^2

AB = SQ.RT 400 = 20

SUFFICIENT

What is the concept behind this?

why do we need to use the squares of the hyp's.? Are we some how using the pythagorean theorem?

Let there be two similar triangles ABC and PQR. Let us call the ratio of corresponding sides as scale factor (SF).

PPTY(1) The perimeters of two similar triangles are in the ratio of their scale factor.

PPTY (2) The areas of two similar triangles are in the same ratio as the square of their scale factors.

According to PPTY (2), in the given problem, the scale factor (SF) happens to be the ratio of the hypotenuse. It doen't have to be the hypotenuse always (could be any side).

Hence, A1/A2 = AB^2/KL^2

You can find more information on similar triangles from here:

http://www.pinkmonkey.com/studyguides/s ... 505701.asp
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