Step by step
The question
Question: A lunch costs $36.
The tip is 18%.
What is the total cost?
1 Find the tip
Percent means out of 100.
So 18% is 18 divided by 100: 0.18.
The point moves 2 places to the left.
18% = 18 ÷ 100 = 0.18
The tip is 18% of $36.
"Of" means times: 0.18 times $36.
That is $6.48.
tip = 0.18 × $36 = $6.48
To multiply decimals: first 18 times 36, as whole numbers.
That is 648.
Then count the decimal places: 2.
So it is 6.48.
18 × 36 = 648
2 decimal places: 6.48
Careful!
18% is not $18.
It is 18% of the price.
Careful: not $36 + $18 = $54 ✗
2 Add it on
The tip is added to the price.
$36 plus $6.48 is $42.48.
total = $36 + $6.48 = $42.48
So the total is $42.48.
3 Check
Let's check another way: we pay 100% plus 18%: 118% of the price.
1.18 times $36 is $42.48.
The same.
So the answer is right!
100% + 18% = 118%: 1.18 × $36 = $42.48
Let's look back.
First: find the tip.
Then: add it on.
Last: check.
Answer
total = $36 + $6.48 = $42.48