A1. Sara and Klara together have 816 euros. If Sara spent $\frac{3}{5}$ of her money and Klara $\frac{3}{7}$ of her money, they would both have the same amount left. How much money does Sara have?
(A) 408 euros
(B) 366 euros
(C) 336 euros
(D) 480 euros
(E) 816 euros
A1. Let $x$ be the amount of Sara's money and $y$ be the amount of Clara's money. Then $x+y=816$ and $\frac{2}{5} x=\frac{4}{7} y$. From the second equation, we express $x=\frac{10}{7} y$ and substitute it into the first equation. This gives us $\frac{17}{7} y=816$. Therefore, $y=336$ and $x=480$. Sara has 480 euros.