A chemist has 100 ml of 25% acid solution. how much of the solution does she need to drain and replace with 70% acid solution to obtain 100 ml of 60% acid solution?

The proportion of acid at 70% that the chemist must use will be 77.8%, while the remaining 22.2% will be acid at 25%.

Step-by-step explanation:

Since the chemist has 100 ml of solution with 25% acid, and wants to obtain a solution of 60% acid by mixing the first with another 70% acid solution, to determine how much of each solution the chemical should use necessary to perform the following calculation:

70 x 1 + 25 x 0 = 70

70 x 0.9 + 25 x 0.1 = 65.5

70 x 0.8 + 25 x 0.2 = 61

70 x 0.7 + 25 x 0.3 = 56.5

Therefore, the proportion to be used is between 70% and 80% of acid at 70%, and 20% to 30% of acid at 25%.

70 x 0.75 + 25 x 0.25 = 58.75

70 x 0.76 + 25 x 0.24 = 59.2

70 x 0.77 + 25 x 0.23 = 59.65

70 x 0.78 + 25 x 0.22 = 60.1

Thus, the proportion should be between 77 and 78% of acid at 70% and 22 and 23% of acid at 25%.

70 x 0.778 + 25 x 0.222 = 60.01

Thus, finally, the proportion of acid at 70% that the chemist must use will be 77.8%, while the remaining 22.2% will be acid at 25%.

given the equation is 8+9z=-6, the first step would be to subtract the 8 from both sides:

8+9z-8=-6-8

since 8 minus 8 = 0, this would cancel out the 8. and since -6 minus 8 equals -14, the equation would look like this

9z = -14

the answer is 15 to your question