Problem Solving Task
Jennifer, Rory, and Wayne were all born two years apart. Jennifer is the oldest, and Wayne is the youngest. The sum of their ages is 39. How old is Rory?
Solution and Discussion:
This problem is similar to “consecutive integer” problems commonly presented in pre-algebra. Those who are comfortable with variables would likely solve for a variable. However, with Rory being the middle child, a common mistake would be to forget to add 2 to the youngest age to find Rory’s age.
Here is a sample bar model solution. It supports visualization of the situation and the difference in ages. It also supports algebraic thinking and attention to the variable for which the student is solving in the end. Practice in this type of approach leads to fewer mistakes of the type mentioned earlier. The Matholia Bar Model tool can help students develop these visualizations.