Questions about the world of GRE Math from other sources and general math related questions.
baily106
Course Students
 
Posts: 49
Joined: Sat May 03, 2014 1:13 am
 

Official Guide - p. 262, q. 14 - diagonal of 3-d rectangle

by baily106 Sun Jun 08, 2014 7:28 pm

Question 14 on page 262 has a figure that I cannot draw on here. I would like to know how does one find the diagonal (AB) of a rectangular sold when the height is 2, the length is 10 and the width is 7.

Thanks,
Anisha
tommywallach
Manhattan Prep Staff
 
Posts: 1917
Joined: Thu Mar 31, 2011 11:18 am
 

Re: Official Guide Book Question

by tommywallach Mon Jun 09, 2014 11:28 pm

Hey Anisha,

You can actually do Pythagoras in three dimensions. You would think they would've taught this in the lesson, but they don't (silly official guide!):

a ^ 2 + b ^ 2 + c ^ 2 = d ^ 2

7 ^ 2 + 2 ^ 2 + 10 ^ 2 = d ^ 2

49 + 4 + 100 = d ^ 2

153 = d ^ 2

d = rt. 153 = rt. 9 * rt. 17 = 3 rt. 17

Hope that helps!

-t
baily106
Course Students
 
Posts: 49
Joined: Sat May 03, 2014 1:13 am
 

Re: Official Guide - p. 262, q. 14 - diagonal of 3-d rectangle

by baily106 Tue Jun 10, 2014 2:21 pm

I didn't not know that; it helps a lot.
Thank you!
tommywallach
Manhattan Prep Staff
 
Posts: 1917
Joined: Thu Mar 31, 2011 11:18 am
 

Re: Official Guide - p. 262, q. 14 - diagonal of 3-d rectangle

by tommywallach Fri Jun 13, 2014 2:46 pm

Glad to help!