5. The soil for planting contains 12% water. Dora wants to plant decorative plants that require a soil moisture level of $28 \%$. How much water needs to be added to 5 kg of the purchased soil to successfully plant the flowers?

## Tasks worth 10 points:
First method:

In 5 kg of purchased soil, there is $88 \%$ dry matter, i.e., $5 \cdot 0.88=4.4 \mathrm{~kg}$.

2 POINTS

The mass of the dry matter will remain the same after adding water.

Let $x$ kg (liters) of water be added to the $5 \mathrm{~kg}$ of soil.

Then, $4.4=0.72(5+x)$.

2 POINTS

$\Rightarrow x=\frac{0.8}{0.72}=\frac{80}{72}=\frac{10}{9}=1.1$ liters.

2 POINTS

TOTAL 6 POINTS

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