Cube dimensions

The red cube has an edge 0.2 dm smaller than the blue cube. The surface of the blue cube is 294 cm². What are the dimensions of the cubes?

Final Answer:

a =  7 cm
b =  5 cm

Step-by-step explanation:

$$\begin{gathered} S=294{\text{cm}}^2 \\ S=6a^2 \\ a=\sqrt{S/6}=\sqrt{294/6}=7\text{cm} \end{gathered}$$

$$\begin{gathered} x=0.2\text{dm}\to \text{cm}=0.2\cdot 10\text{cm}=2\text{cm} \\ b=a-x=7-2=5\text{cm} \end{gathered}$$

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