Data Sufficiency

rishab1988 wrote:Not that I'm bragging.But I have got q51 two times in GMAT quant,so I'm kind of used to such tricks in the question.Doing MGMAT quant and LSAT CR can improve your score a lot because they improve your critical thinking skills.Infer only what you can infer.DO NOT ASSUME ANYTHING

This way you are not so easily tricked by the question...

The answer obviously cannot be C,as explained by nightreader and by me,in my previous post.

If you guys carefully read my explanation you'll know why the answer is NOT C.

Did you bother reading posts by Tomada and Night reader ?

Yes and his reasoning is flawed for the following reasons.

Then we're told that angle BCA = 2*DCA = 40. Thus, angle C = 20+40 = 60. by tomada.

Night reader is correct

but from 1 we know that angle DCA=20

Also looking at the figure angle BCA is SAME as angle C!

Then how did he infer "Thus, angle C = 20+40 = 60"?.

got it?

now we know angle DAC=20 for triangle DAC is isosceles.The only way it is isosceles is when DAC is 20!

Noe get to triangle ABC

We know angle C=40
We wanna find out y

and angle B = 20+ some value[say z]

so y+20+z+40=180
y+z=120

Now if z=100

then y=C=40!

and if z=20 to give angle B=C=40

then y=100

SEE Y took 2 VALUES 40 as well as 100!

rishab1988 wrote:Yes and his reasoning is flawed for the following reasons.

Then we're told that angle BCA = 2*DCA = 40. Thus, angle C = 20+40 = 60. by tomada.

Night reader is correct

but from 1 we know that angle DCA=20

Also looking at the figure angle BCA is SAME as angle C!

Then how did he infer "Thus, angle C = 20+40 = 60"?.

got it?

now we know angle DAC=20 for triangle DAC is isosceles.The only way it is isosceles is when DAC is 20!

Noe get to triangle ABC

We know angle C=40
We wanna find out y

and angle B = 20+ some value[say z]

so y+20+z+40=180
y+z=120

Now if z=100

then y=C=40!

and if z=20 to give angle B=C=40

then y=100

SEE Y took 2 VALUES 40 as well as 100!

Oh yeah!
I went with C=60.
Thanks !

Happy to help....

BTG has been very helpful for me.Can't say about others.

After solving these questions,from wide no of sources and wide levels of difficulty,I have become more versatile.

I dunno about others,but I hate repetition and I always got bored solving those worthless questions from OG.

My theory says,whenever you see anything out of the ordinary,you,almost always,stumble.Therefore,it's very important to be versatile.

Keep it up BTG.

Keep posting tough questions.

Geva you hit the nail on the head.

I pointed out the same error in inference as you did.

rishab1988 wrote:Geva you hit the nail on the head.

I pointed out the same error in inference as you did.

yeah - saw only later that I was busting down a door that's already open, so deleted the post.