Question

John's sister went shopping with him. She expected to spend $100 on clothes, but spent only $10. John wanted to help her calculate the percent error, but he thinks he may have made a mistake. Are his calculations below correct? Why or why not? Ratio = |$100 − $10| $90 = 10 90 ≈ 11%

Answer 1

Answer: Sample response: John’s calculations are not correct. He compared the exact value to the absolute error. The absolute error should be in the numerator and the exact value in the denominator.

Answer 2

Answer: Yes, he applied formula incorrectly.

Explanation:

The formula for percent error is given by :-

`\text{Percent error}=\frac{|\text{expected value-actual value}|}{\text{actual value}}*100`

Given : Expected value = $100

Actual value = $10

Then,

`\text{Percent error}=\frac{\text{10}}*100\\\\=(90)/(10)*100=900\%\\eq11\%`

So, Yes, the calculation did by him was incorrect .