(3) The other known factor is that the water will be added to 300 ml of 70%.

The 300-ml, because it pertains to the 70%, is placed on the line opposite the 70% on

the matrix (see above). Once there are two values on the line and two values on

another line, these values form the proportion.

IF

4

=

300

3

X

Cross Multiply:

4 X

=

900

X

=

225 ml of O% (Water)

they will contain zero percent (0%) active ingredient.

b. Example 2: How many grams of coal tar must be added to one pound of 2%

coal tar ointment to make a 4% coal tar ointment?

Reduced:

(1) This problem indicates a desired strength of 4% and a lower

strength of 2%. If no other strength is indicated, it can be assumed to be 100

percent. Coal tar is 100% coal tar.

(2) Because the question asks, "How many grams of coal tar?" and coal tar

is 100%, the X must be placed on the line opposite 100% (see above).

MD0802

2-35

Integrated Publishing, Inc. |