Step-by-step Solution:

We are given that fresh grapes contain 90% water and dried grapes contain 20% water.
We need to find the weight of dry grapes obtained from 20 kg of fresh grapes.
Step 1: Find the weight of non-water content in fresh grapes
Fresh grapes are 90% water, so the non-water portion (actual grape pulp) is: \[ \text{Non-water content} = 100\% - 90\% = 10\% \] The weight of non-water content in 20 kg of fresh grapes: \[ \frac{10}{100} \times 20 = 2 \text{ kg} \] Step 2: Find the weight of dried grapes
Dried grapes contain 20% water, so the non-water content in dried grapes is: \[ 100\% - 20\% = 80\% \] Let the weight of dried grapes be X kg. Since the non-water portion remains the same (2 kg): \[ \frac{80}{100} \times X = 2 \] \[ X = \frac{2 \times 100}{80} = 2.5 \text{ kg} \] The weight of dry grapes obtained from 20 kg of fresh grapes is 2.5 kg.