To prepare 1000 g of 80% alcohol into 60% alcohol, a student added 300 g of water without consideration If the water is not excessive, how many grams of 20% alcohol should be added? If the water is excessive, how many grams of 95% alcohol should be added?

1000*80%/(1000+300)=61.5%
So the water is not too much. Not enough
Water shortage, add 20% alcohol x G
There are
(1000*80%+x*20%)/(1000+300+x)=60%
The solution is x = 50
So you need to add 50 grams

In order to prepare 1000 grams of 6% alcohol solution and 300 grams of 5% alcohol solution, how many grams of 9% alcohol solution and water are needed?

Use equations to solve
Suppose that 9% brine x g and water y g are added
300+x+y=1000
300*5%+9%x=1000*6%
∴x=500
y=200

1000 grams of 80% alcohol is mixed into 60% alcohol, and someone adds 300 grams of water without thinking. (1) explain whether the water is excessive through calculation. (2) if the water is not excessive, how many grams of 20% alcohol should be added? (1) explain whether the water is excessive through calculation. (2) if the water is excessive, how many grams of 95% alcohol should be added? Please give me your advice

(1) The original mass of alcohol is 1000 * 0.8 = 800g, and the concentration after adding 300 water is 800 / 1300 * 100% = 61.54%, so there is no excess water
(2) Let XG be added, then (0.2x + 1000 * 0.8) / (1000 + 300 + x) = 0.6, and x = 50g,
Your condition is not clearly written in the back, let's add water as Ag, if 800 / (1000 + a)

1000 g 80% alcohol is prepared into 60% alcohol, 300 g water is added first, and then 20% alcohol is added
Polaris_ zhl:
Your answer is the same as that in the book, but I still don't understand the process. What is the x you set? How did 4 come from?

Alcohol water
800 200
800 500
800+x 500+4x
2(800+x)=3(500+4x)
10x=100
x=10
ans=50g

To prepare 1000 g of 80% alcohol into 60% alcohol, a student added 300 g of water without consideration If the water is not excessive, how many grams of 20% alcohol should be added? If the water is excessive, how many grams of 95% alcohol should be added?