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## Topic 3: Calculations  For these questions, you need to use one of the four operations; addition (+), subtraction (-), multiplication (×) or division (÷).

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.

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)

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

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)

This makes sense. The trailer is 10.2m long.

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)

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

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)

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

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