Aquarium

There are 15 liters of water in a block-shaped aquarium with internal dimensions of the bottom of 25 cm and 30 cm. Find the area of water-wetted surfaces. Express the result in dm square.

Correct answer:

S =  29.5 dm²

Step-by-step explanation:

$$\begin{gathered} a=25\text{cm}\to \text{dm}=25:10\text{dm}=2.5\text{dm} \\ b=30\text{cm}\to \text{dm}=30:10\text{dm}=3\text{dm} \\ V=15\text{l} \\ {S}_1=a\cdot b=2.5\cdot 3=\frac{15}{2}=7.5{\text{dm}}^2 \\ V=a\cdot b\cdot c=S_1\cdot c \\ c=V/S_1=15/7.5=2\text{dm} \\ S=S_1+2\cdot c\cdot (a+b)=7.5+2\cdot 2\cdot (2.5+3)=29.5{\text{dm}}^2 \end{gathered}$$

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