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Question about alligation

by Cora
(Oak Park, CA, USA)

How many grams of petrolatum should you add to 30 g of hydrocortisone 2.5% ointment to reduce its strength to 2.0%? The percent strength of petrolatum is zero.

Comments for
Question about alligation

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Sep 04, 2011
The correct answer
by: Keith

Using an alligation for this one is possible. However, an Algebra equation is more practical.
Here's the set-up
30(0.025) = (30+X)(0.02)

Do the math, and X = 7.5
and Grams is the variable we were working with.

Answer = 7.5 grams

Sep 04, 2011
please provide the correct answer
by: Anonymous

I too calculated 7.5g to be the answer. Please provide the correct answer. Having comments is not useful unless we actually know the correct answer.

Aug 16, 2011
tic tac toe?
by: Anonymous

2.5 2 parts of 2.5%
2
0 0.5 parts of 0%

2.5 total parts
0.5/2.5= 0.2

0.2 x 30g= 6 grams

Aug 06, 2011
NOT 0.25
by: Anonymous

NOT USING ALLIGATION
30*0.025= X*0.02.
IT'S NOT 0.25

Jul 09, 2011
I did not do a allegation.
by: Anonymous

IV*IS=FV*FS so 30g*.25=FV*.02
multiply 30*.25=7.5
then divide 7.5/.02
equals 375 grams of %2.0
so 375-30=345
add 345 grams

May 28, 2011
Please check
by: Anonymous

I got 7.5 grams.

Is this correct?

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