# BAR MODEL METHOD in PSLE Math

Ho Soo Thong Ho Shuyuan

# BAR MODEL METHOD in PSLE MATH

** **

In the write-up “*Euclidean Algorithm – A Bar Modelling Approach*”, we illustrate a Line modelling approach to solving two word problems.

In Singapore, school teachers use rectangular bars instead of line segments for a better visual bar model to depict a problem. They use a solving strategy, known as *Ratio Approach*, for a wide range of problems involving ratios, fractions and simple percentages.

To follow up, we will solve some recently PSLE question to illustrate the *Ratio Approach.*

The modelling approach, providing a visual aid for understanding and solving the problem, is known as the ** Bar Model Method**.

** Bar Model Method** involves Two Major Steps:

1. Construct a holistic bar model for visible *Algebraic Relations*.

2. Apply *Simple Arithmetic Computations *and* Simple Algebra *for unknowns.

*Ratio Approach* **to Recent PSLE Questions**

First, we illustrate with solutions to four PSLE 2019 questions involving ratios, fractions and percentages. Pupils can refer to the published Past Examination Papers for the original questions.

**Example 1 – **PSLE (13/01A/19)

The question involves three situations:

1. Algebraic Relation : Number of stars in First Box = Number of stars inSecond Box .

2. First Box : Number of gold stars : Number of silver stars = 1 : 5 .

3. Second Box : Number of gold stars : Number of silver stars = 1 : 2 .

Notes :

1. The problem solving strategy is a direct counting method based on the Part-Whole Concept.

2. The solution involves a simple “*multiple*” algebraic relation.

Here, we have an variant of the above PSLE question for practising the bar modelling ratio approach.

**Exercise 1**

There are two types of cookies in a small box and a large box.

The ratio of the number of sugar cookies to oatmeal cookies is 2 : 3 in the large box and is 2 : 7 in the small box.

The total number of cookies in the small box is 60% of the number cookies in the large .

What fraction of the cookies in the two boxes are sugar cookies?

**Example 3 - **PSLE 09/02/19

The question involves an activity and two situations.

Before Situation : Number of boys : Number of girls = 4 : 1.

Activity : Add 6 boys and 6 girls

After Situation : Number of boys : Number of girls = 3 : 1.

**Example 4 – **PSLE 8/02/2019

Solution to the harder PSLE question is shown in the write-up “*Bar Model Approach To PSLE-2019 Questions*”.