A certain medicine is given in the amount proportional to a patient's body weight. Suppose a patient weighing 164 pounds requires a 205 milligram of medicine. What is the weight of a patient who requires 173.75 milligrams of medicine?

Answer 1

Set up a proportion equation:
m = kw, where m is the amount of medicine, and w is the body weight, k is a constant

for m = 205, w = 164
205 = k(164)
k = 205/164 = 5/4

m = (5/4)w

when m = 173.75,
173.75 = (5/4)w
w = 139

or

just use a simple ratio:
w/164 = 173.75/205
w = 164(173.75/205)
= 139