Model Drawing (Basics)

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1

Model Drawing

• Models are pictorial representations (i.e. bar diagrams) drawn to represent the data in a problem sum.

• It allows us to visualize the relationship between the parts and/or whole in a problem sum.

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Problem Solving Tips

• Read the question carefully.

• Underline important information.

• Transfer the information/data into a model.

• Use a ? to represent the unknown data.

• Label the model with names of the people/things in the question.

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Types of Models

• Part-whole (i.e. for one person) 30 stamps

Ali

?

• Comparison (i.e. for comparison between two people) 30 stamps 2

Ali Don many stamps as Ali. North View Primary School

?

Part-whole model

• A box of cereal costs $7. How many such boxes of cereal can Kelly buy with $42?

$42 ? boxes • $7 $42 ÷ $7 = 6 She can buy 6 boxes of cereal.

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Comparison Model

1 • Bala has the amount of money Alyssa has. Bala has thrice the amount of money Catherine has. If the total amount of money they have is $50, how much money does Alyssa have?

?

A B C

$50

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?

A B C

10 units  $50 1 unit  $50 ÷ 10 = $5 6 units  $5 x 6

= $ 30

She has $30.

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$50

Other models

• ‘Stack Up’ Model • ‘Constant Difference’ Model • Before & After Model These models are improvisation of the part whole and/or comparison models.

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•

‘Stack Up’ Model

2 dictionaries and 4 novels cost $90. Each dictionary cost thrice as much as each novel. How much did each dictionary cost?

?

D D N N N N North View Primary School

$90

D D N N N N

10 units  $90 1 unit  $90 ÷ 10 = $9 ?

$90 3 units  $9 x 3

= $ 27

Each dictionary cost $27.

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‘Constant Difference’ Model

• There was 14 kg of rice in Box A and 2 kg of rice in Box B. Tommy added an equal amount of rice into each box. Now there are 5 times as much rice in Box A as in Box B. How much rice is there in Box A in the end?

14 kg

Box A Box B

2 kg 12 kg

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14 kg ?

Box A Box B

2 kg 14 kg – 2 kg = 12 kg 4 units  12 kg 1 unit  12 kg ÷ 4 = 3 kg 12 kg 5 units  3 kg x 5 = 15 kg There is 15 kg of rice in Box A.

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Before & After Model

• John and Ivan had an equal number of sweets. After John gave away 36 sweets, Ivan had 5 times as many stamps as John. How many stamps did Ivan have?

Ivan John

Before ?

Ivan John

After 36

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?

Ivan John

36 4 units  36 1 unit  36 ÷ 4 = 9 5 units  9 x 5 = 45 Ivan had 45 sweets.

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