Answer: The biologist should mix 20 cc of the 40% solution and 5 cc of the 10% solution to obtain 25 cc of a 34% solution.
Explanation:
Let x be the amount of 40% solution and y be the amount of 10% solution.
We want to find x and y such that:
x + y = 25 cc
0.4x + 0.1y = 0.34 * (x + y)
Substituting the first equation into the second one, we get:
0.4x + 0.1(25-x) = 0.34 * 25
0.4x + 2.5 - 0.1x = 8.5
0.3x = 6
x = 20 cc
Substituting x in the first equation, we get:
20 + y = 25
y = 5 cc
Therefore, the biologist should mix 20 cc of the 40% solution and 5 cc of the 10% solution to obtain 25 cc of a 34% solution.