The day you begin to store a watermelon in your basement it weighs 10 pounds and is 99% water. You forget about it for a while and when you bring it up from the basement, it is 98% water. What does it weigh?
At first, you had 99% water. So, you had 10 x 99% = 9.9 mass of water and 0.1 dry mass.
The dry mass is always constant.
Then, you have 98% weight water. This means that the 2% is dry mass, and is equal to 0.1.
Find for 100%, using proportions.
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