(3) The other known factor is that the coal tar must be added to one pound

of 2% ointment. Because the answer is to be grams, the value one pound must be

changed to 454 grams and placed on the line opposite 2%. Once two values are on

one line and two values are on another line, these values will form the proportion.

IF

1

THEN

X

48

=

454

cross multiply

48 X = 454

X = 9.4583333 grams of coal tar (100%)

(can be rounded to 9.46 g)

Problems Involving Ratio Strengths:

c. Example 3: How many milliliters of water should be added to 500 ml of a

1:200 potassium chloride solution to make it a 1:4000 solution?

(1) The ratio strengths do not have to be changed to percentages to work

this problem. Instead, they may be changed to whole numbers by multiplying each ratio

by the largest denominator.

(2) The largest denominator of the two ratios in this problem is 4000,

therefore each ratio should be multiplied by 4000.

1 = 4000 = 1

4000 X

4000 4000

MD0802

2-36

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