by kamran_veg45 Tue Sep 08, 2009 12:37 am
It's data sufficiency, all you need is:
x + y + xy/100 = 9.2
since video cameras in 1995 equals:
1000*(1+x/100)(1+y/100)
1000*(1 + y/100 + x/100 + xy/10,000)
you factor out a 1/100 from the equation and you are left with:
1000/100*(100 + (y + x + xy/100))
Now, knowing the information we have from (2) => x + y + xy/100 = 9.2:
10(100+9.2) = 1092
Therefore, B is sufficient and A is completely useless (as A does not tell us anything about x and y).
I don't think you need to do all that factoring nonsense LOL..and you can do this question in under a minute! And I agree with Luci, questions in the 2nd gmat prep were a lot easier, I thought.
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I think the guest confused himself/herself as he did all the intricate calculations, because it's clearly mentioned in the question that x + y + xy/100 = 9.2 and the guest comes out with the answer: x + y + xy/100 = 99.08 ! He/she, for some reason, claimed that 1000*(1+x/100+y/100+xy/10,000) = 9.2, which is WRONG! The portion inside the bracket equals 9.2 as explained above! According to the guest, the video cameras in 1995 equal 9.2...WRONG! Please read carefully.
Also, GMAT 2007, please have a look at your factoring! There is a mistake in the underlined portion in between the bold steps:
= (100+x)(10+y/10) = (100+x)(100+y)/10 = 10000+10(x+y) + xy/10 = 10(1000+(x+y)+xy/100)
The 1/10 outside the bracket applies to the entire bracket, so the 10000+10(x+y) + xy/10 should actually be 1000+10(x+y) + xy/10 and the final equation should actually be: 10*(100 + (y + x + xy/100)) as mentioned earlier!
Besides that, all is correct :)
-Hope this helps!