To conduct a scientific experiment, students need to mix 90 mL of a 3% acid solution. They have a 1% and a 10% soulution available. How many mL of each of the two solution must they combine to pruduce 90mL of the 3% solution?

Theoretically they need 90ml & 3% = 2.7ml of 100% solution.

Let x=volume of 10% solution, then
90-x = volume of 1% solution.
x*10% + (90-x)*1% = 2.7
Multiply by 100:
10x + (90-x) = 270
Solve for x and check.
I get 20ml 10% and (90-20)ml 1%.

To find out how many mL of each solution the students need to mix, we can set up a system of equations based on the information given.

Let's say:
x = mL of the 1% acid solution
y = mL of the 10% acid solution

We know that the total volume of the solution is 90 mL, so we can write the equation:
x + y = 90 ...(Equation 1)

We are also given that they need to mix a 3% acid solution. The acid concentration of each solution is given in percentages, so we can use those to set up the equation for the concentration of acid in the mixture. The amount of acid in the 1% solution is 0.01x, and the amount of acid in the 10% solution is 0.1y. The total amount of acid in the mixture is 0.03(90), since they want a 3% acid solution.
0.01x + 0.1y = 0.03(90) ...(Equation 2)

Now, we can solve this system of equations by substitution or elimination.

Let's solve it using the substitution method:
From Equation 1, we have: x = 90 - y

Substituting this into Equation 2:
0.01(90 - y) + 0.1y = 0.03(90)
0.9 - 0.01y + 0.1y = 2.7
0.09y = 1.8
y = 1.8 / 0.09
y = 20

So, they need 20 mL of the 10% acid solution.

Substituting this back into Equation 1:
x + 20 = 90
x = 70

Therefore, they need 70 mL of the 1% acid solution.

In conclusion, they need to mix 70 mL of the 1% acid solution and 20 mL of the 10% acid solution to produce 90 mL of the 3% acid solution.

To determine how many milliliters of each solution the students need to combine, we can set up a system of equations based on the concentrations and volumes of the solutions.

Let's denote the volume of the 1% solution as x mL and the volume of the 10% solution as (90 - x) mL, as the total volume required is 90 mL.

The equation for the concentration (C) of a solution can be calculated by multiplying the volume (V) of the solution with its corresponding percentage (P), and then dividing by the total volume (T). Therefore, we can write the following equation based on the given information:

(1% solution concentration) + (10% solution concentration) = (3% solution concentration)

(0.01 * x) + (0.1 * (90-x)) = 0.03 * 90

Now, we can solve the equation to find the value of x (the volume of the 1% solution).

0.01x + 9 - 0.1x = 2.7

-0.09x = 2.7 - 9

-0.09x = - 6.3

Dividing both sides of the equation by -0.09:

x = -6.3 / -0.09

x ≈ 70

Therefore, the students need to mix 70 mL of the 1% solution and (90-70) = 20 mL of the 10% solution to produce 90 mL of the 3% acid solution.