A student weighed some raisins and recorded the weight as 'x'. She then soaked the raisins in distilled water. After about 2 hours she removed the raisins, wiped them dry and weighed again and recorded that as 'y'. The percentage of water absorbed by raisins may be determined using the relationship

To determine the percentage of water absorbed by the raisins, we calculate the ratio of the mass of water absorbed to the initial dry mass of the raisins, and then convert it into a percentage.

1. Initial weight of dry raisins = $x$
2. Final weight of swollen/soaked raisins = $y$
3. Weight of water absorbed by the raisins = $\text{Final weight} - \text{Initial weight} = y - x$
4. Percentage of water absorbed = $\frac{\text{Weight of water absorbed}}{\text{Initial dry weight}} \times 100 = \frac{y-x}{x} \times 100$

Why other options are incorrect:

• Option A: This divides the weight of water absorbed by the final wet weight ($y$), which is incorrect because the baseline for absorption must be the initial dry weight ($x$).
• Option C: This divides by 100 instead of multiplying by 100, which gives a fraction rather than a percentage.
• Option D: This only multiplies the absolute weight gain by 100 without dividing by the initial dry mass, which does not represent a percentage of the initial mass.