Chapter 10 Math 281
Proportions
A proportion is an equation with a ratio on each side. To use a propor-
tion, the ratios must be equal to each other.
Example: 8:4 = 2:1.
Another way of expressing this is 8/4 = 2/1 or:
8
=
2
4 1
One way proportions are used by healthcare professionals is in deter-
mining dosages of medicine.
Example: John is a 150-pound man. The dosage directions
for one of John’s medications is to give a 150-pound man
10 milliliters (ml) of the liquid medicine. What if John weighed
300 pounds (lb)? What dosage would he be given then? A pro-
portion can be used to fi nd the answer.
150
=
300
10 x (or unknown)
Cross multiply to begin solving for x. Multiply the numerator of the
fi rst fraction by the denominator of the second. Repeat this step with the
numerator of the second fraction and the denominator of the fi rst. In this
case, you end up with:
150x = 3000
To fi nd the value of x, divide 3000 by 150.
3000/150 = x
x = 20
A 300-pound man would need 20 ml of the medication to receive
the proper dose.
Using a Calculator
Healthcare workers are required to perform math calculations when
doing various tasks such as determining medication dosages, working in
a healthcare facility’s accounting department, or determining the salt con-
tent of a low-sodium diet. Even though calculators are on hand in most
cases, it is important to understand the fundamentals of mathematics. You
proportion
a statement of the equality
of two ratios
Ratios and Proportions
1. The Eastridge Hospital Emergency Department reported that 1 out of
6 patients arriving on the second Saturday in December had the fl u. If
78 people were admitted, how many of these patients had the fl u?
2. If 1:16 patients on a hospital fl oor need special meals, and there are
64 patients on the fl oor, how many special meals should the kitchen
prepare?
Real Life Scenario