Five students spent 12, 15, 9, 20 and 14 minutes on a homework task…

Step by step

The question

Question: find the mean of 12, 15, 9, 20 and 14.

The mean is the fair share.

We add them all, then share the total equally.

There are four choices.

First we solve it, the normal way.

Then we pick.

1 Add them all

We add all the numbers, from left to right.

So the total is 70.

2 Count them

Now we count the numbers.

There are 5.

3 Share equally

We share the total equally: 70 divided by 5.

70 divided by 5 is 14.

4 Check

Let's check: if every number were 14, 5 of them would make 14 times 5.

That is 70, the total.

So it is right!

5 Pick the choice

Our answer is mean = 14.

That is choice B.

6 Why not the others

A is 70.

Wrong: that is the total: divide it by 5.

C is 11.

Wrong: that is the range.

D is 17.5.

Wrong: divided by 4: there are 5 times.

Let's look back.

First: add them all.

Then: count them.

Then: share equally.

Then: check.

Then: pick the choice.

Last: why not the others.