Questions about the world of GRE Math from other sources and general math related questions.
Alexander
Course Students
 
Posts: 18
Joined: Wed Dec 03, 2014 3:43 am
 

OG p 260 #7 - Similar Triangle missing side

by Alexander Mon Dec 15, 2014 7:09 pm

Hi - I'm confused why method 2 doesn't work. What am I missing?

Thanks!

1) Cross Multiply

s = length of XZ

I got this correct. 6/4 * 9/s --> 36 =6s --> s = 6


2) Ratio

XY:PQ = 9:6 = 3:1

If side PR is 4 then XZ is 3 times larger = 12
tommywallach
Manhattan Prep Staff
 
Posts: 1917
Joined: Thu Mar 31, 2011 11:18 am
 

Re: OG p 260 #7 - Similar Triangle missing side

by tommywallach Tue Dec 16, 2014 5:52 pm

Hey Amh,

Similar only means they have the same ratios of side to side. So you can say the ratio of PQ: PR = XY: XZ, but can't connect up XY to PQ. Those are two different triangles. Similarity doesn't tell you anything about the relationship between two different triangles, only that the INTERNAL relationships of each triangle are the same.

-t