5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
gmatprep..urgent help needed
This topic has expert replies
-
samirpandeyit62
- Master | Next Rank: 500 Posts
- Posts: 460
- Joined: Sun Mar 25, 2007 7:42 am
- Thanked: 27 times
2 exprs from 4 can be selected in 4P2 = 12 ways
now only possibities where the product is of the form
x- (by)^2
are (x+y)(x-y) & (x-y)(x+y) = 2 possibilties
so reqd P = 2/12 =1/6
Hope this is clear
now only possibities where the product is of the form
x- (by)^2
are (x+y)(x-y) & (x-y)(x+y) = 2 possibilties
so reqd P = 2/12 =1/6
Hope this is clear
Regards
Samir
Samir
2 expresion picked from another 4 = 4!/[(4-2)!*2!] = 6
The only expresion that results in a x^2-(by)^2 form is (x+y)*(x-y), there is no way to say that (x-y)*(x+y) is another way since multiplication is a conmutative operation.
The only expresion that results in a x^2-(by)^2 form is (x+y)*(x-y), there is no way to say that (x-y)*(x+y) is another way since multiplication is a conmutative operation.
-
samirpandeyit62
- Master | Next Rank: 500 Posts
- Posts: 460
- Joined: Sun Mar 25, 2007 7:42 am
- Thanked: 27 times
Well both will do here even if u use Combinations, then also u will get the same result.
Regards
Samir
Samir
Hey Samir
Sorry but this is not clear to me.
4P2 = 12 ways but 4C2 = 6
Now you have said that possibities where the product is of the form
x- (by)^2
are (x+y)(x-y) & (x-y)(x+y) = 2 possibilties
so reqd P = 2/12 =1/6
If you use combination then the ans would be 2/6 = 1/3 instead of 1/6
Aorry for the repeated question. As always thanks in advance for your help
Sorry but this is not clear to me.
4P2 = 12 ways but 4C2 = 6
Now you have said that possibities where the product is of the form
x- (by)^2
are (x+y)(x-y) & (x-y)(x+y) = 2 possibilties
so reqd P = 2/12 =1/6
If you use combination then the ans would be 2/6 = 1/3 instead of 1/6
Aorry for the repeated question. As always thanks in advance for your help
-
samirpandeyit62
- Master | Next Rank: 500 Posts
- Posts: 460
- Joined: Sun Mar 25, 2007 7:42 am
- Thanked: 27 times
If we use Combinations then favorable outcome will be only
(x+y)(x-y) = 1 outcome as order would not be important, we can use it here coz multiplication works both ways
so it will be 1/4C2 = 1/6
(x+y)(x-y) = 1 outcome as order would not be important, we can use it here coz multiplication works both ways
so it will be 1/4C2 = 1/6
Regards
Samir
Samir
-
yuri
- Senior | Next Rank: 100 Posts
- Posts: 45
- Joined: Sun Oct 07, 2007 3:54 pm
- Location: Seattle, WA
- Thanked: 1 times
I figured this out today as well (semi-guessed, but got it right). Anyway, I apologize for probably stupid question, but what does this mean??? What are P and C in these:
4P2 = 12 ways but 4C2 = 6
4P2 = 12 ways but 4C2 = 6
-
beeparoo
- Master | Next Rank: 500 Posts
- Posts: 200
- Joined: Sun Jun 17, 2007 10:46 am
- Location: Canada
- Thanked: 9 times
Yuri, it is short-form notation for PERMUTATION and COMBINATION calculations.yuri wrote:I figured this out today as well (semi-guessed, but got it right). Anyway, I apologize for probably stupid question, but what does this mean??? What are P and C in these:
4P2 = 12 ways but 4C2 = 6
For example: 4C2 = "Four choose 2" = 4!/(2!2!)
