5 of 20 kids have a dog. About how many of 300 have a dog?

Step by step

The question

Question: 5 of 20 kids have a dog.

About how many of 300 have a dog?

1 The fraction in the sample

5 out of 20: that is 5/20.

The 20 kids are a sample: a small group that stands for everyone.

5 and 20 can both be divided by 5.

So it is 1/4.

2 Use it for everyone

We expect the same fraction of all 300: 1/4 of 300.

Of means times.

300 divided by 4 is 75.

That is about 75.

Careful!

A sample only shows about how many.

So the answer is a good guess, not an exact count.

So about 75 kids have a dog.

3 Check

Let's check: 75 out of 300.

Divide the top and the bottom by 75: 1/4, the same fraction as the sample.

So the answer is right!

Let's look back.

First: the fraction in the sample.

Then: use it for everyone.

Last: check.