GMAT [rep ds questions

1) you have QPR=30 no information about the other two angles so //insuff
2) you have the exact same info as in 1, that QPR=30

Triangles have 180 degrees combined on their angles. You have 30 for QPR but not any other information so you can't find the other two.

edit: Oh, my bad for the first one, didn't notice it's a right triangle.

For the first question:
We know that PQR + PRQ + QPR = 180 (sum of the angles of the smaller triangle.

We also know that PRS + PRQ = 180 (sum of the angles that form a straight line.

We are asked to solve for PRS - PQR

1) QPR = 30
So PQR + PRQ = 150
and PRQ + PRS = 180
so we can combined those equations and find that PQR = PRS - 30 so we know the difference in the two angles. therefore 1 is sufficient.

2) is telling us exactly the same thing that 1) is (by telling us that the other two angles of the small triangle = 150, then we know that the third angle = 30, just like 1) told us. So, if 1 is suff, then 2 is suff.

Answer is D.

For the second question:

y = (x+a) (x+b)
y = x^2 +xa + xb + ab
y = x^2 + x(a+b) + ab
So, to solve (and therefore graph) this equation, we need to know (a+b) and ab.

1) tells us what (a+b) is but doesn't give us any information about ab so insuff.

2) we know that then x = 0, y = -6. If we plug that into the equation, then:
-6 = 0^2 + x(a+b) +ab
-6 = 0 + 0 +ab
-6 = ab
only tells us about ab, not (a+b), so insuff

together, they tell us (a+b) and ab, so we can solve the equation and figure out the points where x is 0.

Answer is C

Too tired to tackle question 3.

-Carrie

how does PRS + PRQ = 180 (sum of the angles that form a straight line)
Is it because they are the opposite angles that form line QS?

please help with Q3 as well when you are not tired.
thanks

tj123 wrote:how does PRS + PRQ = 180 (sum of the angles that form a straight line)
Is it because they are the opposite angles that form line QS?

s

Yes, the two angles together are line Qs and the angle of one side of a line like that is 180. Sorry I don't have the words to explain it.

I will try to tackle #3 tomorrow.

-Carrie

Q3

question is: (m/r) = (x/y) ??

1) says m/y = x/r
even after cross multiplying or adjusting we cant bring (m/r) to one side.
so insuff

2) (m+x) / (r+y) = x/y
my + xy = rx + xy
my = rx
ie m/r = x/y

So B

thanks. i completely overlooked that simple xy cancellation
its hard to not over analyze these