Answer:
15 ml
Step-by-step explanation:
We are told
Solution A = 15% of water
Solution B = 20% of water
Let's assume, the entire solution = 100ml
We are told that in the beaker we have 10 ml of Solution A already
Mathematically,
100 ml = 15%
10 ml = X
100ml × X = 15 × 10
X = 150/ 100
X = 1.5%
Hence in the beaker, we have 1.5% of water from Solution A
We are asked to find how many ml of solution B must be added to make the solution have 18% of water
Let y = number of ml of solution B
Hence
10 ml × 15%(0.15) = 1.5 ml of water - Equation 1
y ml × 20%( 0.20) = 0.20y ml of water ...... Equation 2
Add up the above equation
10ml + y ml ×18% (0.18) = 1.5 + 0.20y
(10 + y)(0.18) = 1.5 + 0.20y
1.8 + 0.18y = 1.5 + 0.20y
Collect like terms
1.8 - 1.5 = 0.20y - 0.18y
0.3 = 0.02y
y = 0.3/0.02
y = 15ml
Therefore,15mL of solution B must be added to the beaker in order to create a mixture that is 18% water
