|Is making playdough a good way to teach proportional reasoning?|
First, students could make a number a playdough batches that are proportionally related. For example they could start with yellow as the unit of 1, then make a number of colors that are proportionally greater than yellow. For example blue could be two times yellow, green three times yellow, and red four times yellow.
Students could chart the original ingredients on a table and then multiply those ingredients on the same table for each color. Teachers at the younger grades could use whole number ingredients while intermediate teachers may want to use fractional amounts.
Once the proportional batches are created, students could take a close look in many ways. For example, they could roll balls of each color and discuss the proportional sizes of each color. They could write mathematical sentences describing the sizes of each playdough ball. Similarly they could roll each color into strips and look at the lengths too. You could even grow this project out to relate the proportions to the make-up of Planet Earth and have students use the playdough colors to make a model of the Earth's crust and core with correct proportions.
Once you've created your playdough batches, you could then discuss the metaphor that numbers are playdough using the lesson outlined via this link.