TEACHER NOTES:
“Students should learn to make models to represent and solve problems.”9

Teachers should pose problems such as the following:

John is playing with his toys. Each action figure has two legs, and each animal has four legs. Altogether, there are 18 legs. How many action figures and animals does John have?

Students may represent the situation in different ways. Some may draw a picture representing the number of legs. Others may represent the situation using symbols, making a first guess, then adjusting the number of action figures and animals so that the sum of the legs is 18. The examples following show multiple solutions:
2 + 4 + 4 + 4 + 4; 2 + 2 + 2 + 4 + 4 + 4; 2 + 2 + 2 + 2 + 2 + 4 + 4; or
2 + 2 + 2 + 2 + 2 + 2 + 2 + 4.

9 National Council of Teachers of Mathematics. (2000). Principles and standards for school mathematics (p. 95). Reston, VA: Author.