Omar estimated 48 people. There were 64. What is the percent error?

Step by step

The question

Question: what is the percent error, if Omar guessed 48 people and there were really 64?

Percent error says how far off a guess is, as a percent of the real value.

1 Find the error

First: how far off is it?

The bigger one minus the smaller one.

64 minus 48 is 16.

The error is never negative: it is a distance.

2 Compare with the actual

Now we compare the error with the real value.

The error, 16, goes on top.

The actual value, 64, goes at the bottom.

Careful!

We divide by the actual value, 64.

Not by the guess.

The real value is what we compare with.

3 Write it as a percent

16 and 64 can both be divided by 16.

That keeps the numbers small: 1/4.

Percent means out of 100.

4 times 25 is 100.

So we multiply the top and the bottom by 25.

1 times 25 is 25.

25 out of 100 is 25%.

So the percent error is 25%.

The guess was 25% too low.

4 Check

Let's check: 25% of the actual value should give the error.

25% is 0.25.

0.25 times 64 is 16.

That is the error, 16.

So the answer is right!

Let's look back.

First: find the error.

Then: compare with the actual.

Then: write it as a percent.

Last: check.