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3.08 Ratio and Proportion Basic Algebra: One Step at a Time. Page 297 - 300: #6, Extra Problem Dr. Robert J. Rapalje Seminole State College of Florida Sanford, FL 32773
For explanations, examples, exercises, and answers from Basic Algebra, click here!
At first glance, you
may think, “Word Problems!!” However, let me assure you that these are NOT
word problems! They are just “problems with words!” They are very easy
problems that need almost NO explanation. They are useful to everyday life,
and there is nothing difficult about this page. Just set up a proportion
p. 299. # 6. If on the interstate it takes 3 hours to travel 200 miles, how long will it take to travel 750 miles at this rate? Solution: Set up a proportion of either hours over miles, or miles over hours. It doesn’t matter which way you set it up, as long as you do both ratios the same. In either method, begin by letting x = number of hours.
First Method:
Cross multiply:
Second Method:
Cross multiply:
Extra Problem from a rancher in real life!! A rancher has a 25 gal weed sprayer. In mixing some weed killer, she needs to mix 6.5 oz of Roundup per gallon of water. How many cups of Roundup should be mixed with 25 gallons of water? Note: The first solution given here will be the algebraic solution. The second solution is a common sense approach. Solution:
First Method:
Set up a ratio of :
Cross multiply:
How many cups is this?? A cup contains 8 ounces, so divide by 8. If you want to change cups to quarts, divide by 4. If you want to change quarts to gallons, divide by 4 again. This is what you get:
Second method (common sense!):
The recommended mixture is 6.5
ounces per GALLON. You have 25
gallons, so you need 25
times as much. Multiply
If
you want to know how many gallons that is, divide this answer by
4, since there are
4 quarts in a gallon, and
it will be about
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