Cube 5

The surface of the cube is 15.36 dm². How will change the surface area of this cube if the length of the edges is reduced by 2 cm?

Correct answer:

S =  11.76 dm²
S₁ - S₂ =  3.6 dm²

Step-by-step explanation:

$$\begin{gathered} S=6a^2=15.36d{m}^2 \\ a=\sqrt{S\mathrm{/}6}=1.6dm \\ {a}_2=a-0.2=1.4dm \\ {S}_2=6a_2^2=11.76{\text{dm}}^2 \end{gathered}$$

$S_1-S_2=15.36-11.76={\displaystyle \frac{18}{5}}{\text{dm}}^2=3.6{\text{dm}}^2$

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