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I bought the PDF book from GMAT hacks (at www.gmathacks.com) and found the math review to be very helpful. It has been 22 years since I graduated college and I needed to re-learn (and in some cases actually learn) the math. That plus this forum has been great. We will find out how great on Tuesday w...
- by gaggleofgirls
Sun Feb 08, 2009 9:29 pm- Forum: GMAT Math
- Topic: best refresher material
- Replies: 1
- Views: 1394
2^x - 2^(x-2) can only be dealt with by factoring....
= 2^(x-2) * (2^2 - 1) becuase 2^2 * 2(x-2) = 2^2+x-2 = 2^x
= 2^(x-2) (4-1)
= 2^(x-2) * 3
SO
2^(x-2) * 3 = 3 * 2^13
2^(x-2) = 2^13
x-2 = 13
x = 15
-Carrie
- by gaggleofgirls
Sun Feb 08, 2009 9:27 pm- Forum: Problem Solving
- Topic: exponent problem
- Replies: 2
- Views: 1292
q1 - 10% of all motorists exceed the speed limit and get a ticket 20% of the speeders exceed and do not get a tix. That means that 80% of the speeders do get tickets. So 10% of all motorists = 80% of the speeders. 10/80 = x/100 80x = 1000 x = 1000/80 = 10/8 = 5/4 = 12.5% Answer = B As for Q2, I cann...
- by gaggleofgirls
Sun Feb 08, 2009 9:15 pm- Forum: Problem Solving
- Topic: Two difficult questions: Any genius can help
- Replies: 1
- Views: 1257
I prefer to do these as a formula while other prefer to draw these out. When you have three groups (as in this case with Eng, French and German), then the formula is: total - GroupA + GroupsB + GroupC - AB - BC - AC - ABC - ABC + None. You have to subtract those that are in all three groups twice si...
- by gaggleofgirls
Sun Feb 08, 2009 8:57 pm- Forum: Problem Solving
- Topic: Languages
- Replies: 1
- Views: 1295
Because 2^34 - s^28 does not = 2^6 2^34/2^28 = 2^6 So, we need to figure out something useful to do with 2^34 - 2^28 Factor out 2^28 and you get: 2^28 (2^6-1) = 2^28 (63) 2^28 has a whole bunh of 2s as its factors, but 63 is 7 * 3 * 3, So the greatest prime factor of 2^28(63) = 7. Answer = D. -Carrie
- by gaggleofgirls
Sun Feb 08, 2009 8:17 pm- Forum: Problem Solving
- Topic: Greatest prime factor
- Replies: 1
- Views: 1652
For Q11, see attached diagram to help... An equilateral triangle has 3 60 degree angles and 3 equal sides. When inscribed in a circle, the verticies of the triangle will each touche the side of the circle and the midpoint of the circle will be on the line that is the height of the triangle, which is...
- by gaggleofgirls
Sun Feb 08, 2009 5:25 pm- Forum: GMAT Math
- Topic: GMAT Maths ---Please help !!
- Replies: 5
- Views: 2524
I must be tired, because my first thought when I looked at the problem was that, at the very least, It is C, not E because the problems asks what is a + b/ 1) gives us a and 2) gives us b so certainly the combination gives us a + b :) The similar triangles is clearly the right solution where knowing...
- by gaggleofgirls
Fri Feb 06, 2009 10:20 pm- Forum: Data Sufficiency
- Topic: Triangle
- Replies: 7
- Views: 1841
I'll let one of the GMAT tutors address this. They have said that the formula for standard deviation is not something that the GMAT tests for.
-Carrie
- by gaggleofgirls
Fri Feb 06, 2009 8:01 pm- Forum: Data Sufficiency
- Topic: standart deviation
- Replies: 9
- Views: 4456
To add a little explanation. Notice that the correct answer is 3 times the answer you got. That is becuase you chose to have the professor assign 2 projects to student A, then two projects to student B then the remaining 3 to Student C. But there are two other ways the professor can assign the proje...
- by gaggleofgirls
Fri Feb 06, 2009 7:59 pm- Forum: Problem Solving
- Topic: combination (tough)
- Replies: 2
- Views: 2330
I am not sure why you say that 5c1 * 4c1 is not correct?
5c1 = 5
4c1 = 4
5*4 = 20, just like you already worked out.
-Carrie
Oh, and your question is difficult as it says "as above" when there is nothing above, so we don't know the distribution of M&M colors.
- by gaggleofgirls
Fri Feb 06, 2009 3:47 pm- Forum: Problem Solving
- Topic: Combinations
- Replies: 2
- Views: 1259
I am just confused as to why you are setting up a ratio here. 5280 feet in a mile = 5280(1ft) = 1mile 12 in in a foot = 1ft = 12in So 5280(12in) = 1mile 63360in = 1 mile This is substituting like you substitute a variable in an algebraic equation. 5280(x) = 1m x = 12i 5280(12i) = 1m 63360i = 1m -Car...
- by gaggleofgirls
Fri Feb 06, 2009 3:31 pm- Forum: Problem Solving
- Topic: ratios
- Replies: 1
- Views: 1219
Just a typo. I have replaced the file with an updated one. Yes, when you factor 16 out of (16*sqrt2 + 32) you get 16(sqrt2 + 2) which is what you need to cancel out the denominator.
-Carrie
- by gaggleofgirls
Fri Feb 06, 2009 2:31 pm- Forum: Problem Solving
- Topic: isosceles triangle
- Replies: 5
- Views: 1708
Given that the right answer is 80, I am guessing that the correct question is a committee of 3 senior officers and 1 junior officer.
That would be 6c3 * 4c1 = 20*4 = 80.
-Carrie
- by gaggleofgirls
Fri Feb 06, 2009 8:23 am- Forum: Problem Solving
- Topic: Prob.
- Replies: 4
- Views: 2670
The number of possible committees = number of ways to chose 2 from the 11 women * number of possible ways to chose 2 from the 9 men.
11c2 * 9c2
(11! / 2!*9!) * (9! / 2!*7!)
(11*10 / 2) * (9*8/2)
(11*5) * (9*4)
55 *36
1980
Answer = E
-Carrie
- by gaggleofgirls
Thu Feb 05, 2009 10:36 pm- Forum: Problem Solving
- Topic: Probability..help
- Replies: 3
- Views: 6113
Re: DS1000 S2 Q16,22,23 - need explaination
16. What fractional part of the total surface area of cube C is red? (1) Each of 3 faces of C is exactly 1/2 red. (2) Each of 3 faces of C is entirely white. So we need to be able to know what fraction of the surface area of each face is red and then we can combined that to find the fraction of the...
- by gaggleofgirls
Thu Feb 05, 2009 10:21 pm- Forum: Data Sufficiency
- Topic: DS1000 S2 Q16,22,23 - need explaination
- Replies: 2
- Views: 3492