a. The main reason to convert units is to satisfy unit equality in a ratio and

proportion problem.

For example: If a syrup contains 250 milligrams of tetracycline in each 5

milliliters of the syrup, how many grams of tetracycline are needed to make four liters of

the syrup?

b.

When put in a proportion, the problem would be set up as follows:

IF 250 mg

=

THEN

X grams

5 ml

4 liters

c.

Prior to cross-multiplying, the units must be the same:

Changes: 250 mg

=

0.25 (g)

4L

=

4000 (ml)

d. Only when corresponding units are the same, may the cross-multiplication

take place:

0.25 g

=

X grams

5 ml

4000 ml

Then: 5(X)

=

0.25 (4000)

5X

=

1000

X

=

200 grams

a. To convert a quantity in the metric system to a larger denomination, move the

decimal to the left.

Smaller to Larger

(S L)

=

Right to Left

(R L)

b.

To convert to a smaller denomination, move the decimal point to the right.

Larger to Smaller

(L S)

=

Left to Right

(L R)

c.

In each rule, the L's are together.

MD0802

1-48

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