Step by step
The question
Question: A desk costs $45.50.
It is 20% off.
What is the sale price?
1 Find the discount
Percent means out of 100.
So 20% is 20 divided by 100: 0.2.
The point moves 2 places to the left.
20% = 20 ÷ 100 = 0.2
The discount is 20% of $45.50.
"Of" means times: 0.2 times $45.50.
That is $9.10.
discount = 0.2 × $45.50 = $9.10
To multiply decimals: first 2 times 4550, as whole numbers.
That is 9100.
Then count the decimal places: 3.
So it is 9.100.
2 × 4550 = 9100
3 decimal places: 9.100
Careful!
The discount is the money we save.
We still pay the rest.
Careful: $9.10 is what we save, not what we pay
2 Take it off
A discount comes off the price.
$45.50 minus $9.10 is $36.40.
sale price = $45.50 − $9.10 = $36.40
So the sale price is $36.40.
3 Check
Let's check another way: we pay 100% minus 20%: 80% of the price.
0.8 times $45.50 is $36.40.
The same.
So the answer is right!
100% − 20% = 80%: 0.8 × $45.50 = $36.40
Let's look back.
First: find the discount.
Then: take it off.
Last: check.
Answer
sale price = $45.50 − $9.10 = $36.40