x = 36 and y = 8, both to the nearest whole number. Find the upper…

Step by step

The question

Question: x = 36 and y = 8, both to the nearest whole number.

Find the upper bound of x ÷ y.

1 Bounds of each number

The number x is 36, to the nearest whole number.

Half a step is 0.5.

So it is from 35.5 up to 36.5.

The number y is 8, to the nearest whole number.

Half a step is 0.5.

So it is from 7.5 up to 8.5.

2 Choose the bounds

Dividing by a bigger number gives a smaller answer.

So the biggest answer is the biggest x divided by the smallest y.

So we use 36.5 and 7.5.

Careful!

A bigger bottom makes the answer smaller.

So the bottom goes the other way.

3 Work it out

With a calculator: about 4.87, to 3 significant figures.

So the upper bound of the answer is 4.87.

4 Check

Let's check.

With the rounded numbers we get 4.5.

The upper bound, 4.87, 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.