1-36. USING CONVERSIONS IN PROBLEMS
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
1-37. CONVERSIONS WITHIN THE METRIC SYSTEM
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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