“In Step Maths” grades 1-6 used to be a popular series among local schools—a far more user-friendly series than the “My Pals Are Here” and ‘Math in Focus” series.
During this haziest and most polluted week in Singapore, while looking out for some teaching tips in some dated teaching guides, I came across the following grade 3 Singapore math question, which looks more like a grade 5 question to me:
A number represented by the letter B, divided by 6 and then added to 6, gives the same answer as when the same number B is divided by 9 and then added to 9. What is the number B?
How would you solve it, using the Singapore model, or bar, method? Give it a try before peeping at the solution below, which is the one given in the guide. Would you accept the teacher’s guide’s solution as one that effectively uses the power of the bar model in arriving at the answer?
A bar-modeled solution to the above grade 3 word problem.
Is there an abuse or misuse of the bar method?
Personally, I’m not too comfortable with the given solution, as I feel it lacks some legitimacy in the effective use of the bar method in arriving at the answer. What do you think? Do you sense a misuse or abuse of the visualization strategy? How would you use the bar method, or any non-algebraic method, in solving this question? Share your thoughts with us on whether the bar method has legitimately been applied to solve this grade 3 word problem.
Reference
Gunasingham, V. (2004). In Step Maths Teacher’s Guide 3A. Singapore: SNP Panpac Pte Ltd.
© Yan Kow Cheong, June 21, 2013.