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# The contents of a bag of marbles consist of 9 green marbles

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The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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Updated on: 16 Mar 2012, 03:35
2
00:00

Difficulty:

25% (medium)

Question Stats:

74% (01:28) correct 26% (01:54) wrong based on 303 sessions

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The contents of a bag of marbles consist of 9 green marbles and 16 blue marbles. How many blue marbles must be removed so that 60% of the marbles in the bag will be green?

(A) 1
(B) 6
(C) 7
(D) 9
(E) 10

Relatively easy question and I think I have a problem with the concept. Can someone please explain?

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Originally posted by enigma123 on 16 Mar 2012, 03:24.
Last edited by Bunuel on 16 Mar 2012, 03:35, edited 1 time in total.
Edited the OA
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Re: Number of green marbles  [#permalink]

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16 Mar 2012, 03:34
enigma123 wrote:
The contents of a bag of marbles consist of 9 green marbles and 16 blue marbles. How many blue marbles must be removed so that 60% of the marbles in the bag will be green?

(A) 1
(B) 6
(C) 7
(D) 9
(E) 10

Relatively easy question and I think I have a problem with the concept. Can someone please explain?

Say we remove x blue marbles, so there will be 9+16-x marbles in the bag. We want 9 green marbles to compose 60% of this number: 0.6(9+16-x)=9 --> x=10.

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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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16 Mar 2012, 06:13
We have 9 green and 16 blue marbles.

60% = 9 green marbles
rest 40% = 6, which needs to blue marbles.

6 should be in the bag, so we need to remove 10 marbles.

IMO E.
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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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02 Jun 2012, 03:00
1
A bit of logic.

9G + 16B = 25

60% of 25 = 15

To have our 15 we have to cut the B and to have 6 to obtain 15. The difference is 10. E is the answer
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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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21 Aug 2012, 10:14
1
I just set it up like this.

9/X marbles = .60 ==> solve for x equals 15 marbles. 25-10 = 15.
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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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22 Sep 2013, 19:38
9 green, 16 blue = 25 marbles
60% = 9 marbles , 100% = 15 marbles
so in 15 9 green and 10 blue
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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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23 Sep 2013, 06:40
I Just did it this way,
Since the bag should contain 60% green marbles and rest Blue Marbles,

x/(9+16) = 60% ==> x= 15 ==> 9+ 6 , so 10 blue marbles will be removed.
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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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21 Jan 2015, 19:33
Hi All,

This question is rooted in basic arithmetic. Since the question asks how many marbles need to be removed and the answers ARE numbers, we can TEST THE ANSWERS until we find the one that "fits."

To start, we have a bag of marbles....
9 green
16 blue
25 total

We're asked to remove blue marbles until the green marbles make up 60% of the bag....

Right now, green marbles make up 9/25 = 36% of the bag, so we clearly need to remove a bunch of blue marbles to change this percentage. Looking at the answers, I'd TEST one of the larger options first...

Let's TEST D....

IF 9 blue marbles were removed, then we'd have...
9 green
7 blue
16 total
9/16 is NOT 60% exactly, but it's pretty close....

Let's TEST E...

IF 10 blue marbles were removed, then we'd have...
9 green
6 blue
15 total
9/15 IS 60%, so this MUST be the answer!

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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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21 Jan 2015, 19:33
Hi All,

This question is rooted in basic arithmetic. Since the question asks how many marbles need to be removed and the answers ARE numbers, we can TEST THE ANSWERS until we find the one that "fits."

To start, we have a bag of marbles....
9 green
16 blue
25 total

We're asked to remove blue marbles until the green marbles make up 60% of the bag....

Right now, green marbles make up 9/25 = 36% of the bag, so we clearly need to remove a bunch of blue marbles to change this percentage. Looking at the answers, I'd TEST one of the larger options first...

Let's TEST D....

IF 9 blue marbles were removed, then we'd have...
9 green
7 blue
16 total
9/16 is NOT 60% exactly, but it's pretty close....

Let's TEST E...

IF 10 blue marbles were removed, then we'd have...
9 green
6 blue
15 total
9/15 IS 60%, so this MUST be the answer!

GMAT assassins aren't born, they're made,
Rich
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Contact Rich at: Rich.C@empowergmat.com

# Rich Cohen

Co-Founder & GMAT Assassin

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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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20 Apr 2018, 13:09
enigma123 wrote:
The contents of a bag of marbles consist of 9 green marbles and 16 blue marbles. How many blue marbles must be removed so that 60% of the marbles in the bag will be green?

(A) 1
(B) 6
(C) 7
(D) 9
(E) 10

Relatively easy question and I think I have a problem with the concept. Can someone please explain?

This question is noting but a foul question. Just apply your common sense. Blue marbles are more than green marbles. Now what you want to do. You want to make green marbles 60%. Just think. In order to do it is asked to remove some blue marbles. we don't know how many marbles we remove to meet the condition. if blue and green marbles are equal , i mean, 9/9............it is 50%......green 50% ...........blue is 50%..........therefore all the option A to D is out. Only option E is left.
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Re: The contents of a bag of marbles consist of 9 green marbles  [#permalink]

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20 Apr 2018, 14:00
(9/(25-x))*100 = 60
900 = 60*(25-x)
900=1500 -60x
x=10
Re: The contents of a bag of marbles consist of 9 green marbles &nbs [#permalink] 20 Apr 2018, 14:00
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