Week 2 Challenge (Number 18, Super Bonus Question!)
-
This is the question: A watermelon is 99% water. You have 100 pounds of watermelon. After a week under the sun, the watermelon had dried down to being 98% water. What is the total weight of the watermelon now? Your answer should be the number only, without units.
This is the solution: The main idea of this problem is to understand that after a week under the sun watermelon has a different weight, and water is 98% of the NEW watermelon's weight, which is not 100 pounds.
To solve our problem, let's find something that was unaltered in all our situation. Let's call the part of watermelon that does not contain water at all the "dry" part, so this "dry" part, after being under the sun for a week, has not changed its weight. At the beginning, the "dry" part of the watermelon was
100%−99%=1%, so since the whole watermelon weighed 100×("dry" part), and it weighed 100 pounds, the "dry" part was 100 pounds/100 =1 pound. Then, after a week, the "dry" part of the watermelon became 100%−98%=2% of the whole watermelon's weight, so 1 pound became 2% of the new watermelon, which is 1/50th. Thus, the weight of the new watermelon is 1 pound x 50 = 50 poundsThis is my question: Using this logic, if the watermelon had dried down to being 50% in one week out in the sun, then the watermelon would be 2 pounds. Does this sound right?
