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What strength of 20 ml alcohol should be added to 10ml of 50

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Re: What strength of 20 ml alcohol should be added to 10ml of 50  [#permalink]

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New post 07 Feb 2014, 02:26
4
3
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

84% (01:43) correct 16% (02:04) wrong based on 131 sessions

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aimlockfire1 wrote:
What strength of 20 ml alcohol should be added to 10ml of 50% alcohol to get an average strength of 20% alcohol.

a)0.5 %

b) 5 %

c) 50 %

d) 5.5 %

e) 0.05 %


20*x + 10*0.5 = (20 + 10)*0.2 --> x = 0.05 = 5%.

Answer: B.

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Re: What strength of 20 ml alcohol should be added to 10ml of 50  [#permalink]

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New post 04 Mar 2014, 01:17
Let the strength be x

Then

20.x/100 + 10.50/100 = 30.20/100

x = 5 % = Answer =B
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What strength of 20 ml alcohol should be added to 10ml of 50  [#permalink]

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New post 14 Dec 2014, 04:53
3
Table notation

-----------------------Alcohol--------Water----------Total
Original solution-------5---------------5--------------10

Adding solution--------x---------------y--------------20

Final solution ----------6--------------24-------------30

so, x=6-5=1, y=24-5=19

(1/20)*100=5%

Differential method

x%-------20%--------50%

20-x/50-20=1/2

10=2x

x=5%

Weighted average

(0.5*10)+(x*20)/30=20/100=1/5

5+20x/30=1/5

100x=5

x=5/100=5%

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Re: What strength of 20 ml alcohol should be added to 10ml of 50  [#permalink]

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New post 14 Apr 2016, 09:53
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Re: What strength of 20 ml alcohol should be added to 10ml of 50  [#permalink]

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New post 14 Apr 2016, 09:57
stonecold wrote:
I think the difficulty here should be 600-700.
Not Easy for Everyone..


The difficulty is not about you or any particular individual. Difficulty levels get updated automatically based on the % of correct attempts.
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Re: What strength of 20 ml alcohol should be added to 10ml of 50  [#permalink]

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New post 13 Oct 2017, 22:07
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: What strength of 20 ml alcohol should be added to 10ml of 50 &nbs [#permalink] 13 Oct 2017, 22:07
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