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4. If n is positive integer, can 15n be divided by 6 ? (1) n can be divided by 3 (2) n can be divided by 2 Statement 1: n can be divided by 3. Now, if n is divisible by 2 --> 15n is divisible by 6 But, if n is not divisible by 2 --> 15n is not divisible by 6 Not sufficient Statement 2: n can be div...
- by Rahul@gurome
Mon Jan 24, 2011 9:20 pm- Forum: Data Sufficiency
- Topic: Five DS questions for practice today. Try !
- Replies: 8
- Views: 1563
3. Is a² + b² + c² = (a + b + c)², a, b, c are all positive integer. (1) a² = b² = 4 (2) 1/a + 1/b + 1/c = 0 Statement 1: a² = b² = 4 Thus, a = b = ±2 Hence, (a + b) = -4 OR 0 OR 4 => (a + b + c) = (c - 4) OR c OR (c + 4) => (a + b + c)² = (c - 4)² OR c² OR (c + 4)² Now, a² + b² + cÂ...
- by Rahul@gurome
Mon Jan 24, 2011 12:31 pm- Forum: Data Sufficiency
- Topic: Five DS questions for practice today. Try !
- Replies: 8
- Views: 1563
Point taken guys.
Even after combining both the statements, (2a - b - 4) need not necessarily to be equal to zero.
- by Rahul@gurome
Mon Jan 24, 2011 12:01 pm- Forum: Data Sufficiency
- Topic: Coordinate geo
- Replies: 13
- Views: 2700
welcomeeyelikecheese wrote:Sorry the OA is 36 indeed. I was doing a weighted average of 25(10)+50(40)/60 which gave me 38. I see the correct method now. Thanks!
- by Rahul@gurome
Sun Jan 23, 2011 11:51 pm- Forum: Problem Solving
- Topic: GMATPrep Average
- Replies: 4
- Views: 1479
Total miles = 10 + 50 = 60 miles When driven in the city, gallons = 10/25 = 2/5 = 0.4 When driven on the highway, gallons = 50/40 = 5/4 = 1.25 Total gallons = 0.4 + 1.25 = 1.65 Therefore, average number of miles per gallon that the car travels = 60 miles/1.65 gallons = 36.36 miles per gallon [spoile...
- by Rahul@gurome
Sun Jan 23, 2011 10:59 pm- Forum: Problem Solving
- Topic: GMATPrep Average
- Replies: 4
- Views: 1479
(1) If p = 13, then 13/3 leaves a remainder of 1. If p = 16, then 16/3 leaves a remainder of 1. So, p may or may not be even, no unique answer. Statement 1 is NOT SUFFICIENT. (2) If p = 13, then 13/6 leaves a remainder of 1. If p = 19, then 19/6 leaves a remainder of 1. It can be seen that p will al...
- by Rahul@gurome
Sun Jan 23, 2011 9:44 pm- Forum: Data Sufficiency
- Topic: average DS :)
- Replies: 2
- Views: 1058
A certain jar contains only b black marbles, w white marble, and r red marble. If one marble is to be chosen at random from the jar, is the probability that the marble chosen will be red greater than the probability that the marble chosen will be white? (1) r/(b + w) > w/(b + r) (2) b-w > r Probabi...
- by Rahul@gurome
Sun Jan 23, 2011 9:17 am- Forum: Problem Solving
- Topic: probability
- Replies: 4
- Views: 1547
If ((13!)^16 - (13!)^8)/((13!)^8 + (13!)^4) = a, what is the units digit of a/(13!)^4? Say 13! = x Hence, a = (x^16 - x^8)/(x^8 + x^4) Take x^8 out of bracket in the numerator and x^4 in denominator. Thus, a = [(x^8)*(x^8 - 1)]/[(x^4)*(x^4 + 1)] = (x^4)*(x^8 - 1)/(x^4 + 1) Now, (x^8 - 1) = (x^4 + 1...
- by Rahul@gurome
Sun Jan 23, 2011 4:34 am- Forum: Data Sufficiency
- Topic: How to solve this one?
- Replies: 3
- Views: 1075
In the xy-plane, does the line with the equation y = 2x - 4 contain the point (a; b) ? (1) (2a - b - 4)(a + 5b + 2) = 0 (2) (4a + 3b - 1)(2a - b - 4) = 0 If the line y = 2x - 4 contains the point (a, b), then b = 2a - 4 Hence, (2a - b - 4) must be equal to zero. Statement 1: Either (2a - b - 4) = 0...
- by Rahul@gurome
Sun Jan 23, 2011 4:02 am- Forum: Data Sufficiency
- Topic: Coordinate geo
- Replies: 13
- Views: 2700
Check the calculation again.uriall wrote:....
10c5-6c5
= 10*9*8*7*6/5*4*3*2 - 6
= 42-6
= 36
You're missing a 6 there.
- by Rahul@gurome
Sun Jan 23, 2011 3:25 am- Forum: Problem Solving
- Topic: Combinatorics, please help!
- Replies: 5
- Views: 1325
If you have 4 bikes and 6 cars, how many combinations of 5 vehicles can you make if every combination of the 5 vehicles must at least contain 1 bike and 1 car? Out of 10 vehicles, there are 6 cars. Hence if you select any 5 cars out of these 10, you'll always have at least 1 car in your selection. ...
- by Rahul@gurome
Sun Jan 23, 2011 3:22 am- Forum: Problem Solving
- Topic: Combinatorics, please help!
- Replies: 5
- Views: 1325
(2) (1/10)^(n-1) < 0.1 But for statement 2 If I plug in 1 for n then (1/10) ^0 = (1/1) = 1 which is greater than .1 If I plug in 2 for n then (1/10)^ 1 = (1/10) = .1 which is equal to .1 If I plug in 3 for n then (1/10)^2 = (1/100) = .01 which is less then .1 wouldn't this be insufficent then? Than...
- by Rahul@gurome
Sat Jan 22, 2011 3:13 pm- Forum: Data Sufficiency
- Topic: OG 12 DS #166
- Replies: 1
- Views: 1137
I can't visualize how we got to 4^16???? I don't understand what to make out of "I think it can be thought of as assigning the children to each distinct gift and not the other way around. " statement. Can you please explain how to get to 4^16? Thanks for your help. We have 16 different gi...
- by Rahul@gurome
Sat Jan 22, 2011 1:36 pm- Forum: Problem Solving
- Topic: combo
- Replies: 14
- Views: 4268
Thanks jaxis for pointing out the difference. Here the gifts are different hence there is exist a much more intuitive and easy method as gmat1011 explained. Quick question for Rahul: In your stick method --- If I put 16 different sticks (each standing for a gift) + 3 separators Then why doesn't (19!...
- by Rahul@gurome
Sat Jan 22, 2011 2:06 am- Forum: Problem Solving
- Topic: combo
- Replies: 14
- Views: 4268
Is there a different to do this? The OA is 319/324. It's exactly the same answer but that expression suggests that there's a different methodology. 6!/6^6 is quite the calculation. I believe the method is same as I explained. The calculation is not at all complicated as it looks. Proceed as follows...
- by Rahul@gurome
Fri Jan 21, 2011 11:37 pm- Forum: Problem Solving
- Topic: Combo
- Replies: 5
- Views: 1102