Martha estimated there were 96 marbles in a jar for a contest. The actual number of marbles in the jar was 118. What was the percent error of Martha's estimation?

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

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

Where:

• Estimated Value = 96 (Martha's estimate)
• Actual Value = 118 (actual number of marbles)

Plugging in the values:

\[ \text{Percent Error} = \left( \frac{|96 - 118|}{118} \right) \times 100 \]

Calculating the absolute difference:

\[ |96 - 118| = 22 \]

Now substituting back into the formula:

\[ \text{Percent Error} = \left( \frac{22}{118} \right) \times 100 \]

Calculating the fraction:

\[ \frac{22}{118} \approx 0.1864 \]

Now, converting this to a percentage:

\[ 0.1864 \times 100 \approx 18.64% \]

Thus, the percent error of Martha's estimation is:

C. 18.64%