January 27, 2014 9:23 PM Subscribe
I'm trying to help my 3rd grader with his math homework, but we are stuck on one problem. I can solve it using Algebra, but I'm trying to figure out how to explain it to him using the Singapore method
that he's taught in school. Note that he hasn't learned how to add negative numbers, which puts a crimp on the methodology.
Problem: In 2 years, Tom will be twice as old as he was 5 year ago. How old is Tom now?
My solution: x+2=2(x-5). If you solve for x, the answer is 12
The Singapore solution? This is where I am stuck. I don't understand how to use the bar ("strip diagram") method to model the problem in a way that a 3rd grader taught the Singapore method can solve.