Question

The dimensions and number of animals are given for different corrals

Answer 1

Suppose that the corrals are rectangular in shape. The formula of the area of a rectangle is

$\begin{gathered} A=lw \\ l\to\text{ length} \\ w\to\text{ width} \end{gathered}$

Therefore, the areas of the four different corrals are

$\begin{gathered} A_1=50\cdot40=2000 \\ A_2=60\cdot35=2100 \\ A_3=55\cdot45=2475 \\ A_4=65\cdot40=2600 \end{gathered}$

Then, divide each area by its corresponding population,

$\begin{gathered} \frac{A_1}{110}=18.1818\ldots<20 \\ \frac{A_2}{115}=18.2608\ldots<20 \\ \frac{A_3}{125}=19.8<20 \\ \frac{A_4}{110}=20=20 \end{gathered}$

Therefore, the only corral that meets the requirement is corral 4, the answer is option D.