12 Days of Christmas GMAT Competition - Day 1: In a jar of 300 marbles

Question

12 Days of Christmas 🎅 GMAT Competition with Lots of Questions & Fun

In a jar of 300 marbles, 98% are red. How many red marbles need to be removed to bring the percentage of red marbles down to 95%?

A. 60
B. 120
C. 160
D. 180
E. 240

Bunuel · Accepted Answer

GMAT Club Official Explanation:

Given that out of 300 marbles, 98% are red, the remaining 2%, or 6 marbles, are of some other color. We need these 6 marbles to constitute 5% (1/20) of the marbles after a certain number of red marbles have been removed. Hence, there must be a total of 6 * 20 = 120 marbles left, and thus 300 - 120 = 180 red marbles must be removed.

Answer: D

Kinshook · Answer

Given:  In a jar of 300 marbles, 98% are red. 
 Asked:  How many red marbles need to be removed to bring the percentage of red marbles down to 95%?

Total marbles = 300
Red marbles = 98%*300 = 294

Let x be number of red marbles to be reduced to bring the percentage of red marbles down to 95%
Total marbles = 300-x
Red marbles = 294 - x
% of red marbles = (294-x)/(300-x) = 95% = .95 = 19/20
6/(300-x) = 1/20
120 = 300 - x
x = 300 - 120 = 180

IMO D

platsmj1 · Answer

98% of 300 is 294 red marbles to begin with. If you subtract 180 from the original 294 you are left with 114 red marbles. You must also subtract 180 from the original total of 300 marbles so you now have 120 marbles in total. Taking the new amount of red marbles (114) and the new total amount of marbles (120) and dividing 114/120 yields 0.95 (multiply by 100 to get 95%).

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amitgangane00 · Answer

Currently the % of red marble is 98% out of 300 marbles. → total red marble = 294 and non red marbles =6
After removing X marbles the % becomes 95%

(294-x)/(300-x)=95/100
29400-100x=28500-95x
900=5x
X= 180

missionmba2025 · Answer

Number of marbles that are not red = 2% of 300 = 06

These marble represent the 5% of the marbles when the red marbles are removed.

\frac{6}{x} * 100 = 5

x = \frac{6}{5} * 100

x = 120

Number of red marbles to remove = 300 - 120 = 180

IMO D

SS.56 · Answer

We can backsolve as well...

Option D
98% of 300=294
300-180=120
294-180=114

New percentage= 114/120= 95%

IMO: D

Lalykys · Answer

- If in the jar of 300 marbles, 98% are red => in the jar we have {98*300/100 red; 2*300/100 blue} = {294 red; 6 blue}
- So the question is, how many red marbles x should we remove to have 95% of red marbles in the jar.
After removing x red marbles the percentage of red marbles can be written like this:
(294-x/300-x ) =95/100 => (294-x)*100 = 95(300-x) => 29400-28500=5x => 5x=900 therefore x=180

so  Answer D

8318507532 · Answer

Options are not matching with my answer please correct me if i am wrong

Total marbles is 300
98% of 300 is 294 ( 294 red marbles)

If we want to make it 95% of red marbles then it would be 285
So we need to remove 9 balls

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snoep · Answer

In a jar of 300 marbles, 98% are red. How many red marbles need to be removed to bring the percentage of red marbles down to 95%?

98% of 300 = 294
 \frac{(294-x)}{(300-x)}  =  \frac{95}{100} 
294 - x = 0.95 (300 - x)
294 - x = 285 - 0.95x
294 - 285 = -0.95x + x
9 = 0.05x
180 = x

Answer: D

BTEO · Answer

Since, no of non-red marbles remains same.
Therefore,
 (2/100)*300 = (5/100)*(300-x)
=> 300-x = 120 
=> x = 180

AviNFC · Answer

No. of red marbles = 0.98 * 300 =294

Let x marbles removed

\frac{294-x}{300-x}  = 0.95

x= 180

Ans D

MayaLove · Answer

Assuming 5% of the new total number of marbles (X) equals 6 marbles (Colours other than Red)

0.05 × X = 6

X = 120

and 120 - 6 (colours other than Red) =  114 Red Marbles .

Initially, there were 294 red marbles. (98% of 300)

and 294 − 114 = 180

12 Days of Christmas GMAT Competition - Day 1: In a jar of 300 marbles

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