Understanding 81807

The aquarium is 0.7m long and 25cm wide. The battery is deep if it can hold no more than 87.5 liters of water. I need help understanding how to calculate this.

Correct answer:

h =  5 dm

Step-by-step explanation:

$$\begin{gathered} a=0.7\text{m}\to \text{dm}=0.7\cdot 10\text{dm}=7\text{dm} \\ b=25\text{cm}\to \text{dm}=25:10\text{dm}=2.5\text{dm} \\ S=a\cdot b=7\cdot 2.5=\frac{35}{2}=17.5{\text{dm}}^2 \\ V=87.5\text{l}\to {\text{dm}}^3=87.5\cdot 1{\text{dm}}^3=87.5{\text{dm}}^3 \\ V=S\cdot h \\ h=V/S=87.5/17.5=5\text{dm} \end{gathered}$$

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