Model Method - Questions and Answers

Question posted by Anissa from the United States:

Grade/Level: Grade 5

Question: Mr Ricci spent 1/3 of his salary on food and 2/5 of the remainder on transport.

*What fraction of his salary did he have left?
*If he had $600 left, find his salary

Answer:

Step 1: Draw a long bar to represent Mr Ricci's salary. Divide it into 3 equal parts. Label 1 part (1/3) as the amount spent on food.

Step 2: Since he spent 2/5 of the remainder of his salary on transport, we need to work out the common multiple of 2 (2 remaining units) and 5 (the remainder of his salary is split into 5 equal parts of which 2 parts are spent on transport). The common multiple of 2 and 5 is 10. Thus, we divide the remainder 2 parts into 10 equal parts.

Step 3: Since 2/5 of the remainder is spent on transport and 2/5 of 10 units is equal to 4 units. Hence, we labelled 4 of the remaining units as spent on transport.

Step 4: Then, the remaining 6 units will be labelled as "Left" and "$600" as that is the part that represent the amount of his salary left. And since each of the 3 big boxes represent 1/3 of his salary and the second and third big boxes have been divided into 5 units each, we will similarly divide the first big box into 5 small units.

Step 5: Then, draw a big bracket below the model to represent his total salary which is equal to 15 units.

From the model,

Fraction left = 6 units out of 15 units = 6/15 = 2/5

Therefore, he had 2/5 of his salary left.

Also,

6 units ----------> $600

1 unit ----------> $600 / 6 = $100

15 units ----------> 15 X $100 = $1500

Therefore, his salary is $1500.