## Thinking Mathematically (6th Edition)

(a) We can find the amount of phosphoric acid in a dosage of 2 teaspoons. $21.5~mg/tsp \times 2~tsp = 43~mg$ There are 43 milligrams of phosphoric acid in a dosage of two teaspoons. (b) $1~oz \approx 30~mL$ $1~tsp = 5~mL$ We can find the number of teaspoons of medicine in the bottle. $4~oz = \frac{4~oz}{1}\times \frac{30~mL}{1~oz}\times \frac{1~tsp}{5~mL}$ $4~oz = 24~tsp$ We can find the amount of phosphoric acid in the bottle. $21.5~mg/tsp \times 24~tsp = 516~mg$ There are 516 milligrams of phosphoric acid in the bottle.