 A ratio is the comparison of two numbers by division.  A classroom has 16 boys and 12 girls.  Also written as16 boys, 16:12 or 16 to girls  Generally, ratios are in lowest terms: 16 = 16/4 = /4 3

 Ratios can compare two unlike things: › Joe earned $40 in five hours › The ratio is 40 dollars or 8 dollars 5 hours 1 hour › When the denominator is one, this is called a unit rate.

Let’s look at a classroom:  Ratios can be part-to-part › 16 boys 15 girls  Ratios can be part-to-whole › 16 boys 31 students

 If a ratio is part-to-whole, you can divide and find a decimal or a percent. › 16 boys 31 students 31/16.00 =.516, or 51.6% are boys

 Proportion is a statement that says two ratios are equal. › In an election, Damon got three votes for each two votes that Shannon got. Damon got 72 votes. How many votes did Shannon get? › Damon 3 = 72 so 3 x 24 = 72 Shannon 2 n 2 x n = 48, so Shannon got 48 votes.

 Tires cost two for $75. How much will four tires cost? › # of tires 2 = 4 so 2 x 2 = 4 tires cost 75 n 75 x 2 $150 n = 150, so four tires cost $150

 One more way to solve proportions:  2 = 6 2 x n = 6 x 8 2n = 48 8 n 2 2 n = 24

 Now you try!  Three cans of soup costs $5. How much will 12 cans cost?  # of cans 3 = 12 3 x 4 = 12 cans cost 5 n 5 x 4 20 dollars n = 20, so 12 cans cost $20

 rithmetic/rates-and- ratios/ratios_and_proportions/v/unders tanding-proportions rithmetic/rates-and- ratios/ratios_and_proportions/v/unders tanding-proportions