Interactive

#### Description:

Students bring in actual receipts and then calculate the sales tax for the purchases and for some variations on the purchases

#### Subjects:

• Mathematics > General
• Mathematics > Arithmetic
• Mathematics > Estimation
• Mathematics > Number Sense & Operations

#### Education Levels:

• Higher Education

#### Keywords:

percents sales tax shopping receipts mental computation

English

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#### Collections:

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#### MAA.1.2.3.5: Mathematics Taxonomy

Percents
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Bohdan Rhodehamel

This activity is a good time to reinforce to students the need to check their work in general, and specifically to continue to develop number sense by performing mental computations to accomplish this. Sales tax is a concept they encounter on a daily basis, and the ability to quickly calculate sales tax, or at least a close approximation, is a skill that may be very useful when they are actually shopping. As sales tax in San Diego is close to 10%, having them think about how much 1/10 of the cost of an item is provides a quick approximation.

You can also have them calculate sales tax for other amounts, say 7.5%. Once they have found 1/10, they can then find many approximations by continuing to halve their resulting amounts (i.e. 7.5% = 5% + 2.5%, etc) and add/subtract them.

Non-profit Tax ID # 203478467