Andy estimated that he would need 80 feet of lumber for a tree house project. He later found that the actual amount of lumber needed was 69 feet. What was the percent error of Andy's estimation?

Question

 A.
11%
 B.
86.25%
 C.
15.94%
 D.
13.75%

Answer 1

To calculate the percent error of Andy's estimation, we use the formula for percent error:

\[ \text{Percent Error} = \left( \frac{\text{Estimated Value} - \text{Actual Value}}{\text{Estimated Value}} \right) \times 100 \]

In this case, the estimated value is 80 feet and the actual value is 69 feet. Plugging in these values:

\[ \text{Percent Error} = \left( \frac{80 - 69}{80} \right) \times 100 \]

Calculating the numerator:

\[ 80 - 69 = 11 \]

Now substitute this back into the formula:

\[ \text{Percent Error} = \left( \frac{11}{80} \right) \times 100 \]

Calculating the fraction:

\[ \frac{11}{80} = 0.1375 \]

Now, multiply by 100 to find the percent:

\[ 0.1375 \times 100 = 13.75 \]

Thus, the percent error of Andy's estimation is 13.75%.

So, the correct answer is D. 13.75%.