Step by step
The question
Question: A phone costs $350.
The sales tax is 7%.
What is the total cost?
1 Find the tax
Percent means out of 100.
So 7% is 7 divided by 100: 0.07.
The point moves 2 places to the left.
7% = 7 ÷ 100 = 0.07
The tax is 7% of $350.
"Of" means times: 0.07 times $350.
That is $24.50.
tax = 0.07 × $350 = $24.50
To multiply decimals: first 7 times 350, as whole numbers.
That is 2450.
Then count the decimal places: 2.
So it is 24.50.
7 × 350 = 2450
2 decimal places: 24.50
Careful!
7% is not $7.
It is 7% of the price.
Careful: not $350 + $7 = $357 ✗
2 Add it on
The tax is added to the price.
$350 plus $24.50 is $374.50.
total = $350 + $24.50 = $374.50
So the total is $374.50.
3 Check
Let's check another way: we pay 100% plus 7%: 107% of the price.
1.07 times $350 is $374.50.
The same.
So the answer is right!
100% + 7% = 107%: 1.07 × $350 = $374.50
Let's look back.
First: find the tax.
Then: add it on.
Last: check.
Answer
total = $350 + $24.50 = $374.50