Problem 3. In $1000 \mathrm{~kg}$ of fresh berries, there is 99% water. During transportation, a certain amount of water evaporated, so the weight of the berries after the water evaporation is $500 \mathrm{~kg}$. What percentage of water do the berries now contain?
Solution. In $1000 \mathrm{~kg}$ there is $\frac{99 \cdot 1000}{100}=990 \mathrm{~kg}$ of water and $10 \mathrm{~kg}$ of dry matter. After transportation, in $500 \mathrm{~kg}$ of strawberries, there is also $10 \mathrm{~kg}$ of dry matter, which means there is $490 \mathrm{~kg}$ of water. Therefore, after transportation, the strawberries contain $\frac{490 \cdot 100}{500}=98 \%$ water.