Fresh grapes contain 80% water by weight, while dry grapes contain only 20% water. If a person has 100 kg of fresh grapes, how many kilograms of dry grapes can be obtained from them after drying?

Question: Fresh grapes contain 80% water by weight, while dry grapes contain only 20% water. If a person has 100 kg of fresh grapes, how many kilograms of dry grapes can be obtained from them after drying?

Solution:
Fresh grapes: 80% water → 20% solid
So, in 100 kg fresh grapes:
Water = 80 kg
Solid = 20 kg
When grapes dry, water evaporates, but the solid remains unchanged.

Dry grapes: 20% water → 80% solid
That means the 20 kg solid must now be 80% of the dry grape weight
So, let total weight of dry grapes = x

Then:
0.8x=20
⇒x=200/0.8 =25 kg