mixing solutions problem

by April
(MI, USA)

How much 75% ethanol is needed to make 300ml of 30% ethanol?
A. 80mL
B. 120mL
C. 180mL
D. 240mL

Would really appreciate it if someone could help me out by writing out the problem (show how to solve). Thank you

Comments for
mixing solutions problem

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Jan 18, 2012
 alcohol
by: Anonymous

want
-----X qty= solution
have

30%
---- X 300 ml= 120 ml
75%
Jan 10, 2012
 simple
by: Riduan

You can do both ways; 75%- - - 30
30%
0%- - - 45

Now, the next step:30/75.300=120 ml

or

(C1)(V1) = (C2) (V2)
(.30)(300) = (.75) (X)
90 /.75 = 120 ml
Oct 27, 2011
 Pharmacy Math Solutions
by: Anonymous

Calculate how much mixture or solution must be given so that the patient receives the correct dose of active ingredient.

Requires 50mg of active ingredient using a 5% w/w mixture
Jul 27, 2011
 there is a short cut
by: Anonymous

Times the two that are close together and divide by the one that is far away!
Jun 29, 2011
 mixing solutions problem
by: Anonymous

How much 75% ethanol is needed to make 300ml of 30% ethanol?
A. 80mL
B. 120mL
C. 180mL
D. 240mL

C1 x V1 = C2 x V2

30% x 300mL = 75% x
9000 = 75x
9000/75 = x
120mL = x

answer B.

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