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
