Pharmacy Tech Study

I am having trouble solving this alligation problem.

Rx: Normal saline. How many milliliters of water must you add to 500ml of a 10% stock solution of sodium chloride to make a batch of normal saline (sodium chloride 0.9% solution)?

Reply (by Keith)

Thanks for the good question. I have asked it on our Facebook Page Like this:

How many milliliters of water must you add to 100ml of a 10% stock solution of sodium chloride to make a batch of normal saline (sodium chloride 0.9% solution)?
A. 578
B. 790
C. 1011
D. none of the above
...
Hint: Formula to use (C1V1=C2V2)
(100)(.10)=(.009)(100+X)
Solve for X
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Try solving it with that formula and comment below with the answer.

Comments for
I am having trouble solving this alligation problem.

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Jan 24, 2012

Riduan
by: Anonymous

easy to do by:
c1.v1=c2.v2
(.10).100=(.009).x
10=.009x
10/.009=x
1111=x
now 1111-100=1011 answer

Sep 25, 2011

i got c
by: Anonymous

(100)(.10)=(.009)(100+x) multiply .009 to 100=.9
then multiply .009 by x
10 = .9 + .009x
10-.9=.009x
9.1=.009x
--- ---
.009 .009
x=1011

Sep 12, 2011

ALLIGATION
by: ebony

I also came up with the same answer which is c.
100x10=1000
1000/0.009= 1111.11

Aug 17, 2011

Answer is D
by: Anonymous

91 mL of water needs to be added to the stock solution to make a normal saline of 0.9%

10% - 0.9% = 9.1mL
9.1mL x 10 = 91mL

Jul 27, 2011

I still don't get it...
by: BT from NC

I still don't get it... ?

Jul 15, 2011

CORRECT ANSWER IS C
by: Anonymous

1000*10/100=10

.9/100=.009

NOW DIVIDE 10 BY.009 AND YOU GET 1111.111

NOW SUBTRACT 100 FROM 111.111 AND YOU GET 1011.11

SO THE ANSWER IS C

Jul 10, 2011

alligation
by: JK...NJ

500ml / .9 pats * 9.1 = 5,056 ml of water

Jun 15, 2011

ANSWER
by: Anonymous

5056 ML

Jun 15, 2011

ANSWER
by: lali

5006 ML

May 29, 2011

I have the answer
by: Anonymous

I got 55.5

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