The 1 kg that isn’t water doesn’t go anywhere. At 98% water it has to be 2% of the total, and 1 kg is 2% of 50 kg. Knock one point off the water and the sack loses half its weight.
Fred has 100 kg of potatoes, and they’re 99% water. He leaves them out overnight and they dry out until they’re 98% water. How much do they weigh now?
Give me a hintThe hint
Follow the part that isn’t water.
Reveal the answerHide the answer
50 kg
Source: Traditional, in David Darling, The Universal Book of Mathematics, 2004