BTGmoderatorDC wrote: ↑

Mon Apr 19, 2021 2:57 pm

What is the difference between the number of windows and the number of doors in the new library?

(1) There are twice as many windows as doors in the new library.

(2) The total number of windows and doors in the library is 96.


OA C

Source: Princeton Review

Both statements are required to solve it.

From 1, we have \(y=2x\). Alone, not sufficient. \(\Large{\color{red}\chi}\)

From 2, we have \(y+x=96\). Alone, not sufficient. \(\Large{\color{red}\chi}\)

Together, we have

\begin{align*}
\begin{cases}
y=2x \\
y+x=96
\end{cases}
\quad
\Longrightarrow
\quad
x=32, \quad y=64 \quad\Large{\color{green}\checkmark}
\end{align*}

Therefore, C