geometery triangle question- only one side given

prasantnaidu: Senior | Next Rank: 100 Posts; Posts: 31; Joined: Tue Aug 19, 2008 11:06 pm; Location: India; Thanked: 1 times; GMAT Score:440

Hi

by prasantnaidu » Wed Jun 10, 2009 12:36 am

Hi Sarang,
The standard formula of finding the ht of a equilateral triangle is
(root 3/2) * side.
So (root 3/2)* side=4 root 3(given)
so side = 8

Thus perimeter= 8*3= 24
Hope that make you happy.
if you want some more ways of solving then you can look here

https://www.beatthegmat.com/gmat-prep-pr ... 10809.html

Keep Rocking,
Prasant.

You don't win the Silver, You lose the GOLD.

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tohellandback: Legendary Member; Posts: 752; Joined: Sun May 17, 2009 11:04 pm; Location: Tokyo; Thanked: 81 times; GMAT Score:680

by tohellandback » Wed Jun 10, 2009 1:37 am

or better remember this
property of a 30-60-90 triangle,
sides will be int he ration 1:sqrt(3):2.
side opp angle 30-1
side opp angle 60-sqrt(3)

same way, 45-45-90 triangle has sides in ratio 1:1:sqrt(2)

The powers of two are bloody impolite!!

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Musiq: Senior | Next Rank: 100 Posts; Posts: 93; Joined: Thu Apr 10, 2008 1:42 pm; Location: Chicago; Thanked: 20 times

by Musiq » Wed Jun 10, 2009 9:27 am

I agree with the posters above that it is very important to know the ratios of sides of standard Right triangles 90/45/45 and 90/60/30.

A good way to know this is being tested is if you see SQRT(2 )or SQRT(3) in the answer choices. That's almost always an indicator that you will need the ratios.

For love, not money.

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