Give each student a bag with 30 or more play-money quarters. Ask how many quarters are in a dollar, which a sixth grade class should have no trouble answering: four. Write this on the board as a ratio of 1:4, explaining this means for every one dollar, there are four quarters. Next, ask students to count out how many quarters there are in two, three and four dollars and have them share their answers. Explain this is a proportion: the number of quarters in any amount of dollars is always four times larger than the number of dollars.
Split students into groups of three or four depending on your class size. Give each group a large sheet of white paper from a paper roll, and the names of five different tall world landmarks, such as the Eiffel Tower or the Sydney Opera House, listing their corresponding heights. Students will make drawings of each landmark using a scale where one inch equals 50 feet. Explain a scale is a proportion between the size of an object on a sheet of paper and in reality. Each landmark should have a proportion written above it in a/b = c/d form.
Split students into groups of four and give each a deck of cards. In this game, students will draw two horizontal lines with an equal sign between them. The dealer will place two cards over and under the left line to make a fraction. Each player gets four cards, and players take turns picking up one card and discarding another. When players are able to make a fraction proportionate to the left card, they'll shout "Proportion!" and collect all the cards. The players will the most cards when all are taken wins. For face cards, Jacks count as 11, Queens as 12 and Kings as 13.
The day before you do this activity, ask students to bring in a copy of a recipe from home that has at least eight different ingredients. To begin the activity, give each student a card with a number from two to six. Students will use proportions to calculate how much of each ingredient they'll need to make the recipe the number of times times given on the card. After all calculations have been made, ask for volunteers to share their answers.