Search found 14 matches
Re: PS 13
If the average (arithmetic mean) of x, y, and 20 is 10 greater than the average of x, y, 20, and 30, what is the average of x and y? A. 40 B. 45 C. 60 D. 75 E. 95 Hi, Answer seems to be wrong for thsi question, so can anyone confirm? (x+y+20)/3 = 10 + (x+y+20+30)/4 4x+4y+80 = 120 + 3x+3y+150 x+y=12...
- by projase
Fri Nov 30, 2007 3:08 am- Forum: Problem Solving
- Topic: PS 13
- Replies: 4
- Views: 1829
For second Qs, I agree with the approach which syv11 has taken. But for 1, I am having some different approach - u can say - We can take 2 apples out of 5 in 5C2 = 10 ways Now 1 of the selected apple should be rotten and it can chosen in only 1 way. The rest one apple can be chosen in = (5 - 1) = 4...
- by projase
Thu Nov 29, 2007 7:35 am- Forum: Problem Solving
- Topic: Probability and rate
- Replies: 3
- Views: 1647
Re: can anyone help~
1≤n≤10, n is a positive integer, n=? 1) The tenth digit of n & 1/n is the same 2) The hundredth digit of n & 1/n is the same answer? and pls kindly explain~~ Thx in advance! Lets take some examples for 1 n=1, then the tenth digit is 0, that is the same of 1/1 n=10, then ...
- by projase
Wed Nov 28, 2007 4:01 am- Forum: Data Sufficiency
- Topic: can anyone help~
- Replies: 2
- Views: 1451
Re: 1
If two copying machines work simultaneously at their respective constant rates, how many copies do they produce in 5 minutes? (1) one of the machines produces copies at the constant rate of 250 copies per minute (2) one of the machines produces copies at twice the constant rate of the other machine...
- by projase
Wed Nov 28, 2007 3:46 am- Forum: Data Sufficiency
- Topic: 1
- Replies: 1
- Views: 2265
Re: 2
A car traveling at a certain constant speed takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 75 km per hour. At what speed, in km/per hour, is the car traveling? answer: 72 1 hour = 3600 seconds and v = d/T T = d/V = 1km/75km/hr = 1/75 hour = 3600/75 seconds ...
- by projase
Mon Nov 26, 2007 3:40 pm- Forum: Problem Solving
- Topic: 2
- Replies: 1
- Views: 1684
Re: help
If x and y are positive integers and 1+x+y+xy=15, what is the value of x+y? answer: 6 What i did to solve this problem was a simple exercise of trial and error. One has the following equation: x+y+x*y = 14 Because the sum of three integers is even, you know that either x, y and xy are even or two a...
- by projase
Mon Nov 26, 2007 3:28 pm- Forum: Problem Solving
- Topic: help
- Replies: 1
- Views: 1454
Re: Manhattan GMAT challenge question
The equations are the followings and we need N.
(1) X = L+T-B+N =4Y
(2) Y=3L+3T-3B=3(L+T-B) =>Y/3 =(L+T-B)
Putting (2) in (1): Y/3+N = 4Y => 11/3*Y=N
The only alternative that is a multiple of 11 is (D).
- by projase
Sat Nov 24, 2007 5:44 am- Forum: Problem Solving
- Topic: Manhattan GMAT challenge question
- Replies: 6
- Views: 1928
Re: Difficult Math Problem #73 - Arithmetic, Number Theory
Those are multiples of 5 and odd numbers... The multiples of 5 between 1 and 1000 are 200 numbers, but you must take only the odd numbers... 5x(1+3+5+...+197+199)=50000. Regards, PR Obtain the sum of all positive integers up to 1000, which are divisible by 5 and not divisible by 2. (A) 1050 (B) 1005...
- by projase
Fri Dec 08, 2006 6:38 pm- Forum: Problem Solving
- Topic: Difficult Math Problem #73 - Arithmetic, Number Theory
- Replies: 3
- Views: 9107
GMATPrep Probability Problem
Four letters are going to be send to four different addresses.
If the letters are to be put into the 4 enveolpes at random, what is the probability that only 1 letter will be put into the envelope with its correct address?
Alt 1/24; 1/8; 1/4; 1/3; 3/8
- by projase
Thu Dec 07, 2006 12:52 pm- Forum: Problem Solving
- Topic: GMATPrep Probability Problem
- Replies: 1
- Views: 3424
Re: Difficult Math Problem #72 - Number Theory
n*2^7*3^2*7^3 should be divisible by 5^2 and3^3.
Then the minimun value of n is 5^2*3=75.
Please comment,
Regards,
PR
800guy wrote:If both 5^2 and 3^3 are factors of n x (2^5) x (6^2) x (7^3), what is the smallest possible positive value of n?
- by projase
Thu Dec 07, 2006 11:12 am- Forum: Problem Solving
- Topic: Difficult Math Problem #72 - Number Theory
- Replies: 3
- Views: 3945
I think the asnwer is 2520, because for the first group, you select 2 people from a group of 8, ie 8 alternatives for the first person and 7 for the second. Because the order doesn't matter you divide by 2!, then 8C2 is already divided by the factorial number. Do you know any reason to divide it aga...
- by projase
Thu Dec 07, 2006 11:06 am- Forum: Problem Solving
- Topic: Difficult Math Problem #68
- Replies: 6
- Views: 4525
Re: OA
A question, why do you divide each combination by the number of groups?. Regards, PR OA: 1st team could be any of 2 guys... there would be 4 teams (a team of A&B is same as a team of B&A)... possible ways 8C2 / 4. 2nd team could be any of remaining 6 guys. There would be 3 teams (a team of A...
- by projase
Wed Dec 06, 2006 2:34 pm- Forum: Problem Solving
- Topic: Difficult Math Problem #68
- Replies: 6
- Views: 4525
Re: Median Coffee blend
I am not sure about your answer... Consider that C=6.5X+8.5Y>=7.3 and X+Y=1 Then 6.5X+(1-X)8.5>=7.3 1.2>=2X 0.6>=X, meaning that "B" is correct... Please comment. #2 One Kilogram of a certain coffee blend consists of X kilogram of Type I coffee and y kilogram of Type II coffee. The cost of...
- by projase
Tue Dec 05, 2006 3:31 pm- Forum: Data Sufficiency
- Topic: Median Coffee blend
- Replies: 4
- Views: 4986
Why is this a permutation problem?
Why is this a permutation and not a combination problem?
For me the solution is 3x 8C3.....
800guy wrote:this is a permutations problem
number of permutations for ONE pizza:
8P3 =
8! divided by (8 - 3)! = 336
multiply this by 3 since there are 3 types of crust
336 x 3 = 1008
hope this helps!!
- by projase
Tue Dec 05, 2006 3:06 pm- Forum: Problem Solving
- Topic: permutations question
- Replies: 7
- Views: 2704