# Estimating Sales Tax without a calculator

by Ty
(Maysville, Mo)

Estimating Sales Tax

You are buying a jacket that cost \$69.95.

If the sales tax rate is 7.75%, would it be more reasonable to expect the sales tax to be about \$4.90 or \$5.60?

### Comments for Estimating Sales Tax without a calculator

 Jan 25, 2013 Sales Tax by: Staff Answer Part I This problem is an example of how to use the Guess and Check Strategy 1. Determine what information the problem provides, along with what you need to find. 2. Select a strategy 3. Solve the problem using your strategy 4. Review your results. Are they reasonable? The sales tax is a multiplication problem. Sales tax = (Cost of Purchase) * (tax rate in decimal form) The decimal form of 7.75% is 0.0775 Sales tax = (\$69.95) * (0.0775) If you had a calculator you would multiply (\$69.95) * (0.0775). However, you can estimate the sales tax without a calculator using several different strategies. This is one of those strategies: To estimate the answer without using a calculator and without completing the multiplication long hand, split the two numbers into parts: 69.95 = 70.00 - .05 0.0775 = .08 - .0025 Sales tax = (\$69.95) * (0.0775) = (70.00 - .05) * (.08 - .0025) At this point, ask youself: is the .05 particularly significant to this problem? Probably not. Drop it from the calculation. = (70.00) * (.08 - .0025) Now, ask youself: is the .0025 significant? Again . . . Probably not. Drop it from the calculation. = (70.00) * (.08) = \$5.60, your rough estimate of the sales tax The real answer is: Sales tax = (\$69.95) * (0.0775) = \$5.42 The rough estimate of \$5.60 is reasonably close.

 Jan 25, 2013 Sales Tax by: Staff ---------------------------------------------------Part IIWhy does this technique work?The answer is the Distributive Property applies to all real numbers.For example, 4 multiplied by 13 is equivalent to 4 multiplied by (7 + 6).Simply put, the Distributive Property states that it makes no difference whether you: multiply 4 times each number individually, and then add the results . . . or . . . add the two numbers together, then multiply the result by 4. The result is the same either way. Thanks for writing.Staff www.solving-math-problems.com