Secondary School Resources

Combining Model Drawing with Algebra

Many Secondary 1 students tend to fall back on model drawing when they attempt word problems needing them to use equations or expressions with algebra. This is because they are often reluctant to shift to new and unfamiliar methods to solve problems, which they believe could be easily solved with model drawing. Yet, secondary schools generally do not accept model drawing as part of the workings. How can you help your child make the shift comfortably? This can be done by building on to what he/she has already learnt. The example below illustrates how you can integrate the features of model drawing and algebra.

Constant- Difference Problem

Dawn is 21 years old and her mother is 45 years old. How many years ago was her mother’s age four times her age?

Model drawing approach

The difference in their ages (24) always remains constant.

The age of Dawn’s mother was four times her age 13 years ago.

Modified approach

Refer to the second diagram and let x replace the unknown number of years required in the question.

The age of Dawn’s mother was four times her age 13 years ago.

Notice that some features of the model drawing approach have been retained; Dawn’s age was represented by 1 unit and her mother’s age was represented by 4 units. The new feature added is the variable, x, which has been used to replace the unknown number of years. Finding the value of x would allow us to solve the problem directly. When your child has become familiar with the algebraic method, the diagram can be omitted.

Read our next article on the Common 3 mistakes made in PSLE Science MCQ Questions. 

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