Six Steps to Model Approach

I will be using this question to illustrate my six step approach in solving problem sum.

Questions

Aminah and Belinda each has some money. If Aminah spends $8, the ratio od the amount of money Aminah has to the amount of money Belinda has becomes 2:3. If Belinda spends $8, the ratio of the amount of money Aminah has to the amount of money Belinda has will be 11:14. How much money do they have altogether?

Answer

Primary 4 Problem Sum

Question

A fruit seller brought 350 apples for $140. 30 apples were rotten. He packed the rest in packets of 4 and sold each packet for $1. How much money did he lose from sale ?

Answer

Primary 4 Problem Sum Question

Question

Gilian spent 1/3 of her salary each month, gave 2/5 of it to her mother and saved the rest. If she saved $400 each month, what is her total salary ?

Answer

Primary 4 Problem Sum ... Suzanne baked tarlets...

Question

Suzanne baked 1200 tartlets. She gave 1/2 of them to her mother and 1/4 of the rest to her sister. How many tartlets did she have left ?

Answer

Primary 4 Problem Sum, ... Two Pails, A and B, ...

Question

Two pails, A and B, contain 1 litre 900 ml of water altogether. After 680 ml of water is poured from pail A into pail B, the amount of water in each pail is the same. How much water was in pail A at first ? Give your answer in litre and ml.

Answer

Introduction

Singapore primary school mathematics has adopted the "Model Approach" in solving "Problem Sum" questions some years ago. I started to learn and practice this method when my daughter was in Primary Five 4-5 years ago and I found it extremely useful. The technique looks very different from the traditional method I learned during my school time. However, once you master the basic I believe all (almost) problem sum questions can be tackled with ease, hopefully :-).

In this blog, I hope to convince you that we do not have to use algebra (eg, x=3y+4, y=x-2) to solve your kid's primary school mathematics. As the proverb says "A Picture Is Worth A Thousand Words", I will use models instead of spending a lot of words in trying to explain how I come to the solution.

A few tips in starting your "model":

• Start drawing blocks on the paper, you don't have to draw in scale. Just draw it neatly.
  
• Label things, people, ...
  
• Put in the known number(s)
  
• Put in question mark(s) to indicate unknown to be found.
  
• Assign a "u" unit for easy reference, if applicable
  
• Do not put too many details in one model, try to use a few models and draw vertical lines to ensure alignment.

Below shows two sample models for most of the typical questions.