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Example 6.45 from Prealgebra, 6.5 Solve Proportions and their Applications
Solve Proportions and their Applications: example 6.45
When pediatricians prescribe acetaminophen to children, they prescribe milliliters (ml) of acetaminophen for every pounds of the child’s weight. If Zoe weighs pounds, how many milliliters of acetaminophen will her doctor prescribe?
Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.
Solution
Identify what you are asked to find. How many ml of acetaminophen the doctor will prescribe Choose a variable to represent it. Let ml of acetaminophen. Write a sentence that gives the information to find it. If 5 ml is prescribed for every 25 pounds, how much will be prescribed for 80 pounds? Translate into a proportion. Substitute given values—be careful of the units. Multiply both sides by 80. Multiply and show common factors. Simplify. Check if the answer is reasonable. Yes. Since 80 is about 3 times 25, the medicine should be about 3 times 5. Write a complete sentence. The pediatrician would prescribe 16 ml of acetaminophen to Zoe. You could also solve this proportion by setting the cross products equal.
Your turn
The book's Try It right after this example: same idea, new numbers. Only the answer is given.
Pediatricians prescribe milliliters (ml) of acetaminophen for every pounds of a child’s weight. How many milliliters of acetaminophen will the doctor prescribe for Emilia, who weighs pounds?
How did it go?