Teresa estimates that the height of a giraffe in a zoo is 18 feet. In fact, it is 16 feet tall. What is Teresa’s percent error? Use proportional relationships to solve the problem. Show all your work and round your answer to the nearest tenth.
To find Teresa's percent error, we need to calculate the difference between her estimate and the actual height of the giraffe and then divide it by the actual height of the giraffe. Finally, we will multiply the result by $100$ to get the percent error.
The difference between Teresa's estimate and the actual height of the giraffe is $18-16=2$ feet.
Dividing this difference by the actual height of the giraffe, we get $\dfrac{2}{16}=0.125$.
Multiplying this by $100$, we find Teresa's percent error is $0.125 \times 100 = \boxed{12.5}$ percent.