Task 1 - 150821 The weighing of a container filled with water resulted in a total mass (container and water mass) of 2000 g. If 20% of the water is poured out, the weighed total mass decreases to 88%.

Calculate the mass of the empty container!
The $12 \%$ taken from the total mass of $2000 \mathrm{~g}$, that is $\frac{12}{100} \cdot 2000 \mathrm{~g}=240 \mathrm{~g}$, is according to the problem exactly $20 \%$, i.e., one fifth of the mass of the water. Since $240 \mathrm{~g} \cdot 5=1200 \mathrm{~g}$, the container therefore contained $1200 \mathrm{~g}$ of water. Thus, the mass of the empty container is $800 \mathrm{~g}$.