You have a 100 kg bag of potatoes. The potatoes are 99% water. You leave the potatoes out overnight and they dry out so they only contain 98% water.
How much do the potatoes weigh now?
50 kg.
Proof
Being 99% water, the potatoes are originally 99 kg water and 1 kg solid. When dried, the solid weight remains the same, but is now 2% of the weight. Thus 1 kg is now 2% \(= \frac{1}{50}\)th of the weight, giving a total weight of 50 kg.