Step by step
The question
Question: A laptop costs $900.
The sales tax is 8.25%.
What is the total cost?
1 Find the tax
Percent means out of 100.
So 8.25% is 8.25 divided by 100: 0.0825.
The point moves 2 places to the left.
8.25% = 8.25 ÷ 100 = 0.0825
The tax is 8.25% of $900.
"Of" means times: 0.0825 times $900.
That is $74.25.
tax = 0.0825 × $900 = $74.25
To multiply decimals: first 825 times 900, as whole numbers.
That is 742500.
Then count the decimal places: 4.
So it is 74.2500.
825 × 900 = 742500
4 decimal places: 74.2500
Careful!
8.25% is not $8.25.
It is 8.25% of the price.
Careful: not $900 + $8.25 = $908.25 ✗
2 Add it on
The tax is added to the price.
$900 plus $74.25 is $974.25.
total = $900 + $74.25 = $974.25
So the total is $974.25.
3 Check
Let's check another way: we pay 100% plus 8.25%: 108.25% of the price.
1.0825 times $900 is $974.25.
The same.
So the answer is right!
100% + 8.25% = 108.25%: 1.0825 × $900 = $974.25
Let's look back.
First: find the tax.
Then: add it on.
Last: check.
Answer
total = $900 + $74.25 = $974.25