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certain quantity of 40% solution is replaced with 25%

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Current Student
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Joined: 11 May 2008
Posts: 555

Kudos [?]: 216 [0], given: 0

certain quantity of 40% solution is replaced with 25% [#permalink]

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New post 28 Jul 2008, 10:54
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

certain quantity of 40% solution is replaced with 25% solution such that the new concentration is 35%. What is the fraction of the solution that was replaced?

(A) 1/4
(B) 1/3
(C) 1/2
(D) 2/3
(E) 3/4


i always screw up on such ones. pls guide....
what quantities to assume and how

Kudos [?]: 216 [0], given: 0

Senior Manager
Senior Manager
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Joined: 06 Apr 2008
Posts: 432

Kudos [?]: 164 [0], given: 1

Re: confusing % [#permalink]

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New post 28 Jul 2008, 11:02
arjtryarjtry wrote:
certain quantity of 40% solution is replaced with 25% solution such that the new concentration is 35%. What is the fraction of the solution that was replaced?

(A) 1/4
(B) 1/3
(C) 1/2
(D) 2/3
(E) 3/4


i always screw up on such ones. pls guide....
what quantities to assume and how


Let the quantity of solution be 1 and x be part of solution replaced

40% of (1-x) + 25% of x = 35% of 1

40 - 40x + 25x = 35

15x = 5

x = 1/3

Kudos [?]: 164 [0], given: 1

Director
Director
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Joined: 20 Sep 2006
Posts: 653

Kudos [?]: 132 [0], given: 7

Re: confusing % [#permalink]

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New post 28 Jul 2008, 11:17
arjtryarjtry wrote:
certain quantity of 40% solution is replaced with 25% solution such that the new concentration is 35%. What is the fraction of the solution that was replaced?

(A) 1/4
(B) 1/3
(C) 1/2
(D) 2/3
(E) 3/4


i always screw up on such ones. pls guide....
what quantities to assume and how



40 (1-x) + 25 = 35

-40x = 35 - 65
x= 3/4 IMO E


EDITED: 40 (1-x) + 25x = 35 IMO B

Kudos [?]: 132 [0], given: 7

Director
Director
avatar
Joined: 20 Sep 2006
Posts: 653

Kudos [?]: 132 [0], given: 7

Re: confusing % [#permalink]

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New post 28 Jul 2008, 12:46
droopy57 wrote:
rao_1857 wrote:
arjtryarjtry wrote:
certain quantity of 40% solution is replaced with 25% solution such that the new concentration is 35%. What is the fraction of the solution that was replaced?

(A) 1/4
(B) 1/3
(C) 1/2
(D) 2/3
(E) 3/4


i always screw up on such ones. pls guide....
what quantities to assume and how



40 (1-x) + 25 = 35

-40x = 35 - 65
x= 3/4 IMO E


EDITED: 40 (1-x) + 25x = 35 IMO B


Why (1-x)?


certain quantity of 40% solution is replaced

total quantity = 1
quantity replaced = x

Kudos [?]: 132 [0], given: 7

Re: confusing %   [#permalink] 28 Jul 2008, 12:46
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certain quantity of 40% solution is replaced with 25%

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