GMAT PREP DS 4

A)

Adb=z
ABD=y

ADB=2x+y=180

x+y+z=180

x+180-2x+z=180

-x+z=0

x=z--(1)

isosceles triangle !! side opp to Z AD=6 similary BD=6

and now 2x and 2x are equal there BC=6

A) angle doesnt help in any ways

its neother 45:45:90 / 30:60:90

IMO A

sparsh.21 wrote:


Please explain...

thanks

it seems i have gone blind

here is another way to solve this:
It uses the rule:
The exterior angle of a triangle = sum of the other 2 interior angles.

So from the figure

BDC = ABD + BAD

So ABD = x. There for Triangle ABD is isoscles.

Stmt 1 says AD = 6
So AD = BD = 6

Triangle BDC is isoscles coz base angles 2x and 2x.
So BC = BD = 6.
Sufficient.

Stmt 2. : we cannot find length of any side from just the angles alone.


So A

vishubn wrote:A)



IMO B

Vishu,
I guess u meant A right ??

vittalgmat wrote:

vishubn wrote:A)



IMO B

Vishu,
I guess u meant A right ??

OOPSIEE!! i always do this !! even sometimes in test

thanks vittal

vishu