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

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

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The content of a bag of marbles consist of green 9 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

The OA is E.

Relatively easy question I'm confused with this PS question, I think I have a problem with the concept. Experts, any suggestion about how can I solve it? Thanks in advance.

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Hi LUANDATO,

We're told that a bag of marbles contains 9 green marbles and 16 blue marbles. We're asked how many blue marbles must be REMOVED so that 60% of the marbles in the bag will be green. We can answer this question by TESTing THE ANSWERS.

To start, since we need 60% of the marbles to be green, we therefore need there to be MORE green marbles than blue marbles... and this means that we have to remove at least 8 of the 16 blue marbles. Thus, the correct answer has to be either D or E.

Let's TEST Answer E: 10 marbles
If we remove 10 blue marbles, then we'll have...
9 green marbles and 6 blue marbles
(green)/(total) = 9/15 = 3/5 = 60%
This is an exact match for what we were told, so this MUST be the answer.

Final Answer: E

GMAT assassins aren't born, they're made,
Rich

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Contact Rich at Rich.C@empowergmat.com

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Quote:
The content of a bag of marbles consist of green 9 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

The OA is E.

Relatively easy question I'm confused with this PS question, I think I have a problem with the concept. Experts, any suggestion about how can I solve it? Thanks in advance.
Hi LUANDATO,
Let's take a look at your question.

There are 9 green and 16 blue marbles in a bag.
Let the 9 green marbles are 60% of a total of 'x' marbles. Then
$$x\times60\%=9$$
$$x\times\frac{60}{100}=9$$
$$x=9\times\frac{100}{60}$$
$$x=15$$

It means that if there are a total of 15 marbles in the bag, only then the 9 green marbles are the 60% of the total marbles in the bag.
Total marbles = 15
Green marbles = 9
We can now calculate the number of blue marbles in the bag.
Blue marbles = 15 - 9 = 6

There were initially 16 blue marbles in the bag, we are asked to find the number of blue marbles that must be removed.
Blue marbles that must be removed = 16 - 6 = 10

Therefore, Option E is correct.

Hope it helps.
I am available if you'd like any follow up.

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LUANDATO wrote:
The content of a bag of marbles consist of green 9 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

The OA is E.

Relatively easy question I'm confused with this PS question, I think I have a problem with the concept. Experts, any suggestion about how can I solve it? Thanks in advance.
If finally x blue marbles are left in the bag then 9 and x must be in the ratio of 60 and 40
That means x/40 = 9/60 or x = 9*40/60=6
Hence 16-6=10 blue marbles must be removed
Option E

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