(from ChatGPT)

To determine how much lighter the potatoes have become after they have
dried out to 98% water content, we can follow these steps:

1. **Initial Condition**:
   - The initial weight of the potatoes is 100 pounds.
   - The potatoes are 99% water and 1% dry matter.
   - Therefore, the weight of the dry matter is \( 1\% \) of 100 pounds, which is 1 pound.
   - The weight of the water is \( 99\% \) of 100 pounds, which is 99 pounds.

2. **Final Condition**:
   - After drying, the potatoes are 98% water and 2% dry matter.
   - The weight of the dry matter remains the same, which is still 1 pound.

   Let's denote the final weight of the potatoes as \( W \)
   pounds. Since the dry matter remains 1 pound and this dry matter
   now constitutes 2% of the total weight, we can set up the following
   equation:

   \[
   0.02 \times W = 1 \text{ pound}
   \]

3. **Solving for the Final Weight**:
   \[
   W = \frac{1}{0.02} = 50 \text{ pounds}
   \]

4. **Finding the Weight Loss**:
   - The initial weight of the potatoes was 100 pounds.
   - The final weight of the potatoes is 50 pounds.

   Therefore, the weight loss is:
   \[
   100 \text{ pounds} - 50 \text{ pounds} = 50 \text{ pounds}
   \]

So, as the potatoes dry out from being 99% water to 98% water, they
become 50 pounds lighter.