Cogito
Consumer Math · Chapter 6 · Lesson 1
Sales Tax and Tips
The price on the shelf is not the price you pay.
12 problems · about 20 minutes · TEKS M.M.6.A
What this lesson teaches
The student computes sales tax, tips, and totals including both.
- Sales tax is added at the register; multiply by 1 plus the rate.
- Tips are computed on the pre-tax bill.
- To undo a tax, divide by 1 plus the rate rather than subtracting.
Warm Up
Straightforward practice. Get the method working first.
5 problemsA $150 item with 6% tax. Total in dollars?
Answer 159
Why $159.
Why does subtracting 8% from a total not recover the pre-tax price?
Answer The 8% was a percentage of the smaller pre-tax price.
Why The two percentages have different bases.
A $200 item with 5% tax. Total in dollars?
Answer 210
Why 200 × 1.05.
A $80 bill with a 15% tip. Tip in dollars?
Answer 12
Why 0.15 × 80.
A $54 total at 8% tax. Pre-tax price in dollars?
Answer 50
Why 54 ÷ 1.08.
Build It Up
The same ideas with more to keep track of.
3 problemsA $60 meal, 8% tax and 18% tip. Total in dollars?
Answer 75.6
Why 60 + 4.8 + 10.8.
10% of $73, to two decimal places?
Answer 7.3
Why Move the decimal point.
A $25 item with 4% tax. Total in dollars?
Answer 26
Why 25 × 1.04.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problemsTo recover a pre-tax price from a total, what should you do?
Answer Divide the total by 1 plus the tax rate.
Why The tax was a percentage of the smaller number.
A $110 total at 10% tax. Pre-tax price in dollars?
Answer 100
Why 110 ÷ 1.10.
The Register: A $50 item with 8% sales tax. Total in dollars?
Answer 54 dollars
Why $54.
The Tip: A $40 bill with a 20% tip. Tip amount in dollars?
Answer 8 dollars
Why $8.