# Problem №2 (10 points)

There are two cubes. The mass of the second is $25 \%$ less than the mass of the first, and the edge length of the second cube is $25 \%$ greater than that of the first. By what percentage does the density of the second cube differ from the density of the first?

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# Solution:

Volume of the second cube
$V=a^{3}=(1.25 a)^{3}$

(4 points)

And its density:

$\rho=\frac{m}{V}=\frac{0.75 m}{(1.25 a)^{3}}=0.384 \frac{m}{a^{3}}$.

(4 points)

That is, the density of the second cube is less than that of the first by $61.6 \%$

(2 points)

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