Grade 7 · Unit 1 · Lesson 2 · part 4 of 6
A proportion, and a peek at the graph
When two ratios are equal, the pair of them has a name: a proportion .
A proportion, and a peek at the graph
When two ratios are equal, the pair of them has a name: a proportion. From the lemonade table, 2 cups cost $1.50 and 4 cups cost $3.00. Both ratios divide to the same number, so they are equal:
That is a proportion: two ratios that are equal. Every pair of rows in a proportional table makes a proportion, because every row divides to the same number. The bowling rows do not: 132 is 6.5 and 183 is 6, so they are not equal, and bowling is not proportional.
A quick look at the graph. Plot the lemonade rows as points, cups across and cost up, and they line up in a straight line that goes right through (0, 0), the point where both amounts are zero. That is the graph test, and Lesson 4 is all about it. For now, just notice that the table test and the graph test agree.