more ds from gmat prep

q18

23x+21y=130

you know that x and y have to be integers; the only set of numbers that solves for 130 total price is x=2 and y=4

Therefore B

If you did not know that x and y have to be integers, you were right

q33

1993 1000
1994 1000*(1+x/100)
1995 1000*(1+x/100)*(1+y/100)=1000*(1+x/100+y/100+xy/10000)

(1) not enough
(2) enough so solution is 1000*(1+9.2/100)

q 33 ==> B

q6

(1) alone is not sufficient, does not tell us anything about (u,v)
(2) try to insert number in 1:

could be u=5, r=-4 and v=5, s=-4 i.e not equidistant or
u=2, r=-1 and v=-1, r=2 i.e. equidistant

If you combine that with statement (1) you will see that all pairs are equidistant; just try a couple more numbers

re: q18
oh, so when I have an unequal # of variables & equations I can guess/plug in as long as I know the variables are integers?

Thats good to know.

thanks

Thank.
Can you explain this part:
how did you go from here:
1995 1000*(1+x/100)*(1+y/100)=1000*(1+x/100+y/100+xy/10000)
TO:
(2) enough so solution is 1000*(1+9.2/100)

1995 1000*(1+x/100)*(1+y/100)=1000*(1+[b]x/100+y/100+xy/10000[/b]) ==> the number in the parenthesis is just multiplying out (1+x/100)*(1+y/100)

Then, you have given x+y+xy/100=9.2 ==> divide by 100 and you get

[b]x/100+y/100+xy/1000=0.092[/b] ==> replace this in the first line and you get

1000*(1+0.092)

Is this clear?

barely.

let me ask you, if you saw this question on the test, how long will it take you
to work out this explanation? Also, did you see from stmt 2 that it might be sufficient or was it while doing the calculations, that you determined B was sufficient?


Thanks