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# John wants to make a 100 ml of 5% alcohol solution mixing a quantity o

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Intern
Joined: 06 Aug 2015
Posts: 48
Concentration: General Management, Entrepreneurship
GMAT Date: 10-30-2016
GPA: 3.34
WE: Programming (Consulting)
John wants to make a 100 ml of 5% alcohol solution mixing a quantity o  [#permalink]

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09 Jun 2017, 10:28
1
00:00

Difficulty:

35% (medium)

Question Stats:

73% (02:06) correct 27% (02:51) wrong based on 102 sessions

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John wants to make a 100 ml of 5% alcohol solution mixing a quantity of a 2% alcohol solution with a 7% alcohol solution. What are the quantities of each of the two solutions (2% and 7%) he has to use?

A) 60
B) 120
C) 30
D) 10
E) 90
Math Expert
Joined: 02 Aug 2009
Posts: 7112
Re: John wants to make a 100 ml of 5% alcohol solution mixing a quantity o  [#permalink]

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09 Jun 2017, 10:41
HARRY113 wrote:
John wants to make a 100 ml of 5% alcohol solution mixing a quantity of a 2% alcohol solution with a 7% alcohol solution. What are the quantities of each of the two solutions (2% and 7%) he has to use?

A) 60
B) 120
C) 30
D) 10
E) 90

total qty = 100..
if avg is 5% and made from 2% and 7%, find the ratio of qty of each by weighted average method..
ratio of 2% = $$\frac{7-5}{7-2}=\frac{2}{5}$$..
so qty of 2% = $$100*\frac{2}{5}=40$$
and of 7% = 100-40=60..
A

HARRY113 you must be looking for qty of 7%..
otherwise qty of both has to be total that is 100
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John wants to make a 100 ml of 5% alcohol solution mixing a quantity o  [#permalink]

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09 Jun 2017, 14:14
HARRY113 wrote:
John wants to make a 100 ml of 5% alcohol solution mixing a quantity of a 2% alcohol solution with a 7% alcohol solution. What are the quantities of each of the two solutions (2% and 7%) he has to use?

A) 60
B) 120
C) 30
D) 10
E) 90

Another way to do weighted average method.

Let A = the volume of the 5% solutions
Let B = the volume of the 2% solution

Volume of resultant mixture is given as 100 ml, so

A + B = 100, and
B = 100 - A

(strength of A)*(Vol of A) + (strength of B)*(Vol of B)
= (strength of resultant mixture)*(Vol of resultant mixture)

.07(A) + .02(B) = .05(100)

Substitute B = 100 - A:

.07(A) + .02(100 - A) = .05(100)

.07A + 2 - .02A = 5

.05A = 3

A = 60 mL and
B = (100 - A) = 40 mL

chetan2u wrote:
HARRY113 you must be looking for qty of 7%..
otherwise qty of both has to be total that is 100

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Joined: 27 May 2012
Posts: 639
Re: John wants to make a 100 ml of 5% alcohol solution mixing a quantity o  [#permalink]

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05 Jul 2018, 09:49
1
HARRY113 wrote:
John wants to make a 100 ml of 5% alcohol solution mixing a quantity of a 2% alcohol solution with a 7% alcohol solution. What are the quantities of each of the two solutions (2% and 7%) he has to use?

A) 60
B) 120
C) 30
D) 10
E) 90

Can Moderator please correct this question ? We are looking for 7% solution and not BOTH 2% and 7% solution.
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Manager
Joined: 23 Nov 2017
Posts: 109
Location: Singapore
Concentration: Strategy, Other
GMAT 1: 660 Q49 V33
Re: John wants to make a 100 ml of 5% alcohol solution mixing a quantity o  [#permalink]

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22 Jul 2018, 22:59
HARRY113 wrote:
John wants to make a 100 ml of 5% alcohol solution mixing a quantity of a 2% alcohol solution with a 7% alcohol solution. What are the quantities of each of the two solutions (2% and 7%) he has to use?

A) 60
B) 120
C) 30
D) 10
E) 90

Isn't the question asks for both the solutions? (which would be 40 and 600) ?
Re: John wants to make a 100 ml of 5% alcohol solution mixing a quantity o &nbs [#permalink] 22 Jul 2018, 22:59
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