|
Author |
Message |
|
TAGS:
|
|
|
Director
Joined: 13 Nov 2003
Posts: 811
Location: BULGARIA
Followers: 1
Kudos [?]:
6
[0], given: 0
|
A certain bag of gemstones is composed of two-thirds [#permalink]
 29 May 2006, 07:32
Question Stats:
53% (01:54) correct
46% (01:12) wrong based on 3 sessions
A certain bag of gemstones is composed of two-thirds diamonds and one-third rubies. If the probability of randomly selecting two diamonds from the bag, without replacement, is 5/12, what is the probability of selecting two rubies from the bag, without replacement?
(A) 5/36
(B) 5/24
(C) 1/12
(D) 1/6
(E) 1/4
|
|
|
|
|
|
|
Intern
Joined: 05 Apr 2006
Posts: 36
Followers: 0
Kudos [?]:
0
[0], given: 0
|
Re: Challenge MHTNGMAT [#permalink]
29 May 2006, 09:03
BG wrote: A certain bag of gemstones is composed of two-thirds diamonds and one-third rubies. If the probability of randomly selecting two diamonds from the bag, without replacement, is 5/12, what is the probability of selecting two rubies from the bag, without replacement?
(A) 5/36
(B) 5/24
(C) 1/12
(D) 1/6
(E) 1/4
is answer 1/12
2/3 * (2X-1) / (3X-1) = 5/ 12 => X = 3
So total gems = 9
and probability of ruby = 1/3 * 2/8 = 1/12
|
|
|
|
|
|
VP
Joined: 29 Dec 2005
Posts: 1356
Followers: 6
Kudos [?]:
17
[0], given: 0
|
Re: Challenge MHTNGMAT [#permalink]
29 May 2006, 09:46
guptaraja wrote: BG wrote: A certain bag of gemstones is composed of two-thirds diamonds and one-third rubies. If the probability of randomly selecting two diamonds from the bag, without replacement, is 5/12, what is the probability of selecting two rubies from the bag, without replacement?
(A) 5/36
(B) 5/24
(C) 1/12
(D) 1/6
(E) 1/4 is answer 1/12 2/3 * (2X-1) / (3X-1) = 5/ 12 => X = 3 So total gems = 9 and probability of ruby = 1/3 * 2/8 = 1/12 this is good enough.........
[{2/3(x)}/x] [{(2x/3)-1}/x-1] = 5/12
x^2-9x = 0
x = 0, 9
so x = 9
diamond = 6
ruby = 3
the prob (2 ruby) = 3c2/9c2 = 1/12
C.
|
|
|
|
|
|
Manager
Joined: 25 Oct 2012
Posts: 215
Concentration: Finance, Entrepreneurship
GPA: 3.54
Followers: 1
Kudos [?]:
37
[0], given: 67
|
Re: A certain bag of gemstones is composed of two-thirds [#permalink]
06 Feb 2013, 17:38
BG wrote: A certain bag of gemstones is composed of two-thirds diamonds and one-third rubies. If the probability of randomly selecting two diamonds from the bag, without replacement, is 5/12, what is the probability of selecting two rubies from the bag, without replacement?
(A) 5/36
(B) 5/24
(C) 1/12
(D) 1/6
(E) 1/4 Let R be the numbers of rubies in the bag, we told that the selection is made without replacement in both cases ( selecting two diamonds or selecting two rubies) Hence, we have : \frac{2}{3}*\frac{2R-1}{3R-1}=\frac{5}{12}So, the number of diamonds in the bag is 6. Likewise, the number of rubies in the bag is 3 and the total of the gemstones is 9. The probability of selecting two rubies from the bag without replacement is : \frac{1}{3}*\frac{2}{8}=\frac{1}{12}Answer : C
_________________
KUDOS is the good manner to help the entire community.
Last edited by Rock750 on 09 Feb 2013, 19:23, edited 1 time in total.
|
|
|
|
|
|
Manager
Joined: 08 Dec 2012
Posts: 50
WE: Engineering (Consulting)
Followers: 0
Kudos [?]:
9
[0], given: 31
|
Re: A certain bag of gemstones is composed of two-thirds [#permalink]
09 Feb 2013, 19:13
Rock750 wrote: BG wrote: A certain bag of gemstones is composed of two-thirds diamonds and one-third rubies. If the probability of randomly selecting two diamonds from the bag, without replacement, is 5/12, what is the probability of selecting two rubies from the bag, without replacement?
(A) 5/36
(B) 5/24
(C) 1/12
(D) 1/6
(E) 1/4 Let R be the numbers of rubies in the bag, we told that the selection is made without replacement in both cases ( selecting two diamonds or selecting two rubies) Hence, we have : \frac{2}{3}*\frac{2R-1}{3R-1}=\frac{5}{12}So, the number of diamonds in the bag is 3. Likewise, the number of rubies in the bag is 6 and the total of the gemstones is 9. The probability of selecting two rubies from the bag without replacement is : \frac{1}{3}*\frac{2}{8}=\frac{1}{12}Answer : C Looks like you got your diamonds and rubies mixed up  though you got it right later
|
|
|
|
|
|
Manager
Joined: 25 Oct 2012
Posts: 215
Concentration: Finance, Entrepreneurship
GPA: 3.54
Followers: 1
Kudos [?]:
37
[0], given: 67
|
Re: A certain bag of gemstones is composed of two-thirds [#permalink]
09 Feb 2013, 19:28
nave81 wrote: Rock750 wrote: BG wrote: A certain bag of gemstones is composed of two-thirds diamonds and one-third rubies. If the probability of randomly selecting two diamonds from the bag, without replacement, is 5/12, what is the probability of selecting two rubies from the bag, without replacement?
(A) 5/36
(B) 5/24
(C) 1/12
(D) 1/6
(E) 1/4 Let R be the numbers of rubies in the bag, we told that the selection is made without replacement in both cases ( selecting two diamonds or selecting two rubies) Hence, we have : \frac{2}{3}*\frac{2R-1}{3R-1}=\frac{5}{12}So, the number of diamonds in the bag is 3. Likewise, the number of rubies in the bag is 6 and the total of the gemstones is 9. The probability of selecting two rubies from the bag without replacement is : \frac{1}{3}*\frac{2}{8}=\frac{1}{12}Answer : C Looks like you got your diamonds and rubies mixed up though you got it right later u are right navy81, thx  Hope this silly mistake had not confused anyone. Anyway, i think it's OK by now 
_________________
KUDOS is the good manner to help the entire community.
|
|
|
|
|
|
|
Re: A certain bag of gemstones is composed of two-thirds
[#permalink]
09 Feb 2013, 19:28
|
|
|
|
|
|
|
|
|
Similar topics |
Author |
Replies |
Last post |
|
Similar
Topics:
|
 |
|
|
In a certain game, a large bag is filled with blue, green,
|
ArvGMAT |
1 |
27 Jun 2007, 20:44 |
|
|
|
|
A certain panel is to be composed of exactly three women and
|
iamba |
2 |
16 Jul 2007, 18:13 |
|
|
|
|
In a certain packinghouse, grapefruit are packed in bags and
|
tarek99 |
3 |
07 Jan 2008, 00:11 |
|
|
2
|
 |
A certain panel is to be composed of exactly three women and
|
mariyea |
5 |
09 Feb 2011, 14:05 |
 |
5
|
|
Certain gemstones are formed by magma, a material found deep
|
iwillcrackgmat |
15 |
12 Mar 2012, 02:30 |
|
|
|
|
|
|
close
