9 of 30 people like jazz. About how many of 900 like jazz?

Step by step

The question

Question: 9 of 30 people like jazz.

About how many of 900 like jazz?

1 The fraction in the sample

9 out of 30: that is 9/30.

The 30 people are a sample: a small group that stands for everyone.

9 and 30 can both be divided by 3.

So it is 3/10.

2 Use it for everyone

We expect the same fraction of all 900: 3/10 of 900.

Of means times.

900 divided by 10 is 90.

Then times 3.

That is about 270.

Careful!

A sample only shows about how many.

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

So about 270 people like jazz.

3 Check

Let's check: 270 out of 900.

Divide the top and the bottom by 90: 3/10, 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.