Grades 7-8 Video Solutions 2024-2024_7-8

Video Transcription

Problem number 18. Water makes up 80% of the mash of fresh mushrooms. However, water makes up only 20% of the mass of dried mushrooms. By what percentage does  the mass of a mushroom decrease during drying? So for example, let's assume that there is a hundred grams of fresh mushrooms. That means that the water will  be 80 grams and the dry matter or whatever is left besides water is 20 grams because we know water is 80% of fresh mushrooms. When we dry the  mushrooms out, the dry matter will not change because only the water content changes when we dry something. And so when we dried, this 20 grams of dry  matter now becomes 80% of the total mass since we know that after drying, water is 20% so dry matter is 80% after drying. So that means that 20 grams of dry matter  is 80% of the mass and so the 20% that is water is 5 grams. I.e. the water has gone from 80 grams to 5 grams during drying. And we know that at the very end  the total mass of the dried mushrooms will be 20 plus 5 equals 25 grams. And so that means that we have decreased the weight of the mushrooms by 75 grams or  75%. That means the answer is C, 75.

Video Summary

The mass of fresh mushrooms decreases by 75% during drying. Starting with 100 grams of fresh mushrooms, which contain 80 grams of water and 20 grams of dry matter, drying reduces the water content. With the original 20 grams of dry matter becoming 80% of the final mass, the dried mushrooms weigh 25 grams: 20 grams of dry matter and 5 grams of remaining water. Consequently, the mass decreases by 75 grams, representing a 75% reduction in mass.

Keywords

mushrooms

drying process

mass reduction

water content

dry matter