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## Topic 3: Calculations

For these questions, you need to use one of the four operations; addition (+), subtraction (-), multiplication (×) or division (÷).

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Whenever you are unsure whether to use one operation or another (e.g. addition or subtraction), try both and write down the answers you get. Only one answer will make sense.

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Here is one of the questions:

A truck and trailer are 14.8m long in total. If the truck is 4.6 m long, how long is the trailer?

The numbers you are given are 14.8 and 4.6. Adding these numbers together gives a total of 19.4 (14.8 + 4.6 = 19.4)

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But the trailer can't be 19.4m long if the truck and trailer are only 14.8m long in total!

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So this tells you that addition was not the right operation to use. Subtracting the smaller number from the larger one gives an answer of 10.2 (14.8 - 4.6 = 10.2)

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This makes sense. The trailer is 10.2m long.

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Here is another question. This time you may be unsure whether to multiply or to divide:

600 students are put into 4 teams for sports day. How many students are there in each team?

The numbers you are given are 600 and 4. Multiplying these numbers together gives a total of 2 400 (600 × 4 = 2 400)

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But there can't be 2 400 students in each team if there are only 600 students altogether!

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So this tells you that multiplication  was not the right operation to use. Dividing the larger number by the smaller one gives an answer of 150 (600 ÷ 4 = 150)

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This makes sense. There are 150 students in each team.

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