Porportions

Porportions

1. Equivalent ratios, fractions, or percents

2. Given a ratio and a whole, find the part

   • 1/3 of the class are girls. There are 30 students in the class. How many girls are in the class?
     • Solutions
       • Multiply the whole by the ratio. e.g. 30 *1/3=10
       • Set up an equivalent ratio 1/3 = ?/30.
   • 30% of the class are girls. There are 30 students in the class. How many girls are in the class?
     • Solutions
       • Convert to an equivalent ratio 30% = 3/10
       • Convert to an equivalent decimal 30% = 0.3 and multiply the whole by the decimal 30 * 0.3 =9

3. Given a ratio and a part, find the whole

   • 1/3 of the class are girls. There are 10 girls in the class. How many students are in the class?
     • Solutions
       • Set-up an equivalent ratio. e.g., 1/3 = 10/?
       • Divide the part by the ratio. e.g. 10 ÷ 1/3 =30
   • 20% of the class are girls. There are 16 girls in the class. How many students are in the class?
     • Solutions
       • Use a bar model
       • Convert to an equivalent ratio e.g. 20% = 1/5
         • Set-up an equivalent ratio e.g. 1/5 = 16/?
         • Divide the part by the equivalent ratio. e.g. 16 ÷ 1/5 = 80
       • Convert to decimal (20% = 0.2) and divide part by decimal 16 ÷ 0.2 = 80

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