Rectangular 7647

There are 140 liters of water in a rectangular aquarium with 800 mm and 50 cm base dimensions. How high in cm does the water level reach? What is the area in dm² of the inner walls of this aquarium up to the water level?

Correct answer:

h =  35 cm
S₂ =  91 dm²

Step-by-step explanation:

$$\begin{gathered} a=800\text{mm}\to \text{cm}=800:10\text{cm}=80\text{cm} \\ b=50\text{cm} \\ V=140\text{l}\to {\text{cm}}^3=140\cdot 1000{\text{cm}}^3=140000{\text{cm}}^3 \\ {S}_1=a\cdot b=80\cdot 50=4000{\text{cm}}^2 \\ h=V/S_1=140000/4000=35\text{cm} \end{gathered}$$

$$\begin{gathered} S=2\cdot (a+b)\cdot h=2\cdot (80+50)\cdot 35=9100{\text{cm}}^2 \\ {S}_2=S\to {\text{dm}}^2=S:100{\text{dm}}^2=9100:100{\text{dm}}^2=91{\text{dm}}^2=91{\text{dm}}^2 \end{gathered}$$

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