Question

12. FIND THE ERROR A student is finding the

total cost c, including sales tax, of a book
that costs $9.95. The sales tax rate is 9%.
Find the student's mistake and correct it.

Answer 1

Here is what the student wrote (re-pasting for clarity)

C = 1.9 x 9.95

C = 18.91

C = $18.91

The error happens in the 1st line

Why? Because the 1.9 should be 1.09

The 1.9 represents a tax of 90% when we want a 9% tax instead

In other words, 9% = 9/100 = 0.09 while 90% = 90/100 = 0.9

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This is what the steps should look like

C = 1.09 x 9.95

C = 10.8455

C = 10.85

Don't forget to round to the nearest hundredth, aka nearest penny.

The total cost, after sales tax, is $10.85