In this issue of Math in the News, we look at back-to-school purchases and the impact that different tax rates have on the total cost.

1. The Math of Back-to-
School Shopping

2. What you will learn
• Summary
• In this issue of Math in the News we look at the prices and
purchases parents and teachers make during back-to-school
shopping
• Determine the price of items before and after tax by
multiplying by percents and decimals.
• Compare prices in a table

3. School Supplies
• Every August and September, schools compile a list of supplies
students will need for school.
• Basic supplies include…
• Pencils
• Paper
• Binders
• Today, kids might also need…
• A computer
• An iPad

4. Money-Saving Tips
• Check out this local news video on how to
save money on school supplies.
• http://newyork.cbslocal.com/2016/08/11/back-
to-school-shopping/

5. The Cost of School Supplies
• School supplies can add up! Especially when you
include the 6% - 8% sales tax (depending on the
state).
• Visit http://taxfoundation.org/article/state-and-local-
sales-tax-rates-2016 to see the sales tax rate in
your state!
• In the next slides, we’ll look at how to find the price
of an item before and after sales tax.

6. What’s the total cost after
sales tax?
• When you see an item at a store and it’s marked
with a price, say $5.25, but that’s not the total cost
you pay. That’s the price BEFORE tax.
• To find the total cost of an item after sales tax,
Price + Tax = Total cost

7. How do you calculate the tax?
• To find the tax, multiply the cost by the sales tax
rate as a percent or a decimal:
Tax = Price x Sales Tax Rate

8. What is the formula for total
cost?
Total Cost = Price + Price • Sales Tax
= Price (1 + Sales Tax)

9. Example 1
Problem
• What is the cost of a notebook that costs $5.25 with a 6%
sales tax?
Solution
Total Cost = Price (1 + Sales Tax)
= 5.25 (1 + 0.06)
= 5.25 • 1.06
= 5.57

10. Example 2
Problem
• Take a look at the pre-tax price of some common back-to-
school items:
• Box of 40 #2 pencils: $4.99
• Plastic Pencil Case: $2.04
• Package of lined paper: $2.54
• Package of 5 binders: $28.99
• What’s the total cost?
Source:http://www.target.com/s?category=0%7CAll%7Cmatchallpartial%7Call+categories&searchTerm=binder

11. Example 2
Solution
• When you have multiple items, first add all the individual
prices to find the Total Price. Calculate the tax on the Total
Price.
Total Price = 4.99 + 2.04 + 2.54 + 28.99 = 38.56
Total Cost = Total Price (1 + Sales Tax)
= 38.56 • (1 + 0.06)
= 38.56 • 1.06
= 40.87

12. Tax-free Holiday!
• As you can see, there’s a big difference
between the before-tax price and the after-tax
price, especially for more expensive items.
• To help families and teachers, many states
participate in a “tax-free” holiday where, for
one weekend, people shop tax-free.
• How much money would you save?

13. Your Turn!
• Take a look at your back to school shopping list. Make
sure you include all items (clothing, electronics, school
supplies, etc).
• Go to http://www.target.com/ or the website of the store
you bought your supplies to find the prices.
• Go to http://taxfoundation.org/article/state-and-local-
sales-tax-rates-2016 to see the sales tax rate in your
state.
• Calculate the Total Price and the Total Cost.

14. What are the savings?
• How much more money did you spend in total
with taxes compared to without taxes?
• What do you notice about how much you pay
in sales tax as the price of an item increases?