A3. The length of the aquarium is $50 \mathrm{~cm}$, the width is $20 \mathrm{~cm}$, and the height is $25 \mathrm{~cm}$. How many $\mathrm{cm}$ from the top edge of the aquarium will the water level be if we pour 19 liters of water into it?
(A) $19 \mathrm{~cm}$
(B) $1,9 \mathrm{~cm}$
(C) $10,9 \mathrm{~cm}$
(D) $6 \mathrm{~cm}$
(E) $0,6 \mathrm{~cm}$
A3. We find that the volume of water is $19 \mathrm{dm}^{3}$. We write the data into the formula for the volume of water ( $x$ is the height of the water $\mathrm{v}$ in the aquarium) and get the equation $V=5 \cdot 2 \cdot x=19$. We calculate $x=1.9 \mathrm{dm}$ $=19 \mathrm{~cm}$. The water level will thus be $6 \mathrm{~cm}$ lower than the top edge of the aquarium. The correct answer is D.