x = 7 and y = 4, both to the nearest whole number. Find the upper…

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The question

Question: x = 7 and y = 4, both to the nearest whole number.

Find the upper bound of x + y.

1 Bounds of each number

The number x is 7, to the nearest whole number.

Half a step is 0.5.

So it is from 6.5 up to 7.5.

The number y is 4, to the nearest whole number.

Half a step is 0.5.

So it is from 3.5 up to 4.5.

2 Choose the bounds

To make the answer as big as it can be, both numbers must be as big as they can be.

So we use 7.5 and 4.5.

Careful!

We do not change the answer by half a step.

We work it out again with the biggest numbers.

3 Work it out

That is 12.

So the upper bound of the answer is 12.

4 Check

Let's check.

With the rounded numbers we get 11.

The upper bound, 12, is more than that, as it should be.

So the answer is right!

Let's look back.

First: bounds of each number.

Then: choose the bounds.

Then: work it out.

Last: check.