Today, coming home from school, he pulled out his Sunshine Math sheet and got to work. (The Sunshine Math program is run by our PTA and is an optional program that students can sign up for at the beginning of the school year. The weekly sheets offer math challenges for students to complete independently. Students get the sheets on Mondays and turn them in to the PTA on Fridays. PTA volunteers correct the sheets and return them to students. Students are rewarded periodically by PTA for their participation and at the end of the year, the teachers host a Math Challenge Day for students to compete.) Most of the time, the questions are rich contextually based problems which promote my child's problem solving skills. However, today, on the back of the sheet, there were a set of problems that looked very traditional.
Now, take a few moments to consider how my son solved it.
Since I knew that they wanted him to get the answer 27, and I was intrigued by his thinking, I wrote the problem 56-29 on a sticky note and asked him to solve. A second later, he handed me back the correct answer of 27. I said, "Tell me how you solved it." He replied, "I know 50-20 is 30 and 6-9 is negative 3, so the equation is 30-3 which equals 27." He used a left to right strategy to solve and is very comfortable with negative numbers. I said, "How did you know 6-9 is negative 3?" He said, "Do you want me to prove it to you on a number line?" He's eight years old!