Problem: Three cans of brand A corn cost π²1.77. Four cans of brand B corn cost π²2.24. What is the difference in cost per can?
Brand A:
\( 1.77 \div 3 = 0.59 \)
Brand B:
\( 2.24 \div 4 = 0.56 \)
Find the difference:
\( 0.59 - 0.56 = 0.03 \)
Answer: Brand A costs π²0.03 more per can.
Example 7: Miles Per Minute
Problem: Aaliyah drove 14 miles in 16 minutes. What was Aaliyah's rate of speed per minute?
βPer minuteβ means miles for 1 minute.
Divide miles by minutes:
\( 14 \div 16 = \frac{14}{16} \)
Simplify:
\( \frac{14}{16} = \frac{7}{8} \)
As a decimal:
\( \frac{7}{8} = 0.875 \)
Answer: \( \frac{7}{8} \), or 0.875, mile per minute
Example 8: Savings with a Pass
Problem: A monthly zoo pass costs π²30. One-day admission costs π²7.50. If a person goes to the zoo 5 times in a month, how much money is saved by buying the monthly pass?
Find the cost without the pass:
\( 7.50 \times 5 = 37.50 \)
The monthly pass costs:
\( π²30 \)
Find the savings:
\( 37.50 - 30 = 7.50 \)
Answer: π²7.50 is saved by buying the monthly pass.
π§ Math Vocabulary
Rate: a comparison of two quantities with different units.
Unit Rate: a rate that compares a quantity to exactly 1 unit.
Equivalent Rate: a rate that describes the same relationship using different values.
Fractional Rate: a rate that includes a fraction, such as \( \frac{3}{4} \) mile per minute.
Ratio Table: a table used to organize equivalent ratios or rates.
Proportion: an equation showing that two ratios or rates are equal.
Unit Cost: the cost for 1 item, 1 pound, 1 ounce, or another single unit.
Per: a word meaning βfor each one.β
π‘ Main Idea
Unit rate problems can appear in many forms, including prices, speed, gas mileage, fractional rates, and savings comparisons. The key is to identify what βper 1 unitβ means and then divide, multiply, or compare equivalent rates as needed.
π What You Should Already Know
Students should know how to divide decimals, multiply decimals, simplify fractions, multiply fractions, compare rates, and interpret words such as βper,β βeach,β and βat that rate.β
π What Comes Next
After reviewing unit rate word problems, students can extend these ideas to proportional relationships, constant of proportionality, percent problems, scale drawings, slope, and linear relationships.
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