 # Bar Model Approach to PSLE-2019 Questions

Ho Soo Thong

Revised Nov 2021

In 2019 PSLE Examination, pupils encountered quite a number of challenging questions.

Here, we intend to highlight the basic mathematics  in a Holistic Bar Modelling Approach to two types of challenging questions :

Ratio (fraction) situations – A Counting Approach with the Greatest Common Unit

Distributive Situations – Mathematics of Distributive Law

A holistic bar model enables us to understand each question and select an effective approach to the solution. Furthermore, we can  see the challenging level of each question.

Question 1 PSLE 8/02/2019

A box contained black beads and white beads. At first, the number of black beads was ⅓ of the number of white beads. After ¼ of the black beads and ⅜ of the white beads were used,63 beads were left.

b)How many beads were there in the box at first?

Solution

# Remark  : The question involves three related “Fraction”situations. There is a complex algebraic relation 3X = 8Y for which we apply the Greatest Common Unit Procedure for a counting approach.

Question 2 PSLE 14/02/19

Kelvin and Julie bought some egg tarts. Each of them spent \$61.20.  Julie got 6 more egg tarts than Kelvin because she used a coupon that gave her  a 15% discount.

(a) How many  egg tarts did Julie get?

(b) What was the price of each egg tart without the discount?

Solution Remark :  A challenging Distributive Problem involves the algebraic relation

Total cost = Unit cost × Number of units

The question can be solved as a Percentage Problem and here we show  a direct ratio approach.