There are two kinds of alcohol, one is 60% and the other is 90%. Now we need to prepare 300 grams of alcohol with 70% concentration. How many grams of alcohol do you need? (200g, 100g)

There are two kinds of alcohol, one is 60% and the other is 90%. Now we need to prepare 300 grams of alcohol with 70% concentration. How many grams of alcohol do you need? (200g, 100g)

Let's take 60% alcohol x g, then take 90% alcohol (300-x) g, then from the question meaning: 60% x + (300-x) 90% = 300 × 70%, the solution is: x = 200. So 300-x = 100. Answer: need 60% alcohol 200 g, 90% alcohol 100 g

Dr. Wang used 95% alcohol solution and 70% alcohol solution to prepare 75% disinfectant alcohol. To prepare 1kg of disinfectant alcohol, how many grams of each alcohol are needed?

Suppose that 95% alcohol solution x g, 70% salt water (1000-x) g, 95% x + 70% (1000-x) = 75% × 1000, & nbsp; & nbsp; & nbsp; & nbsp; 0.95x + 700-0.7x = 750, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 2001000-200 = 800 (g); answer: 95% salt water 200 g and 70% salt water 800 g are needed