Quandaries
and Queries 

Having a problem with word problems. example A chemist mixes a 10% acid solution with a 50% acid solution to form 400mL of a 40% solution. How much of each solution should be used. Need to identify the variables. Thank you 

Hi, You have two solutions, a weak solution (10%) and a strong solution (50%). You need to mix some of the weak solution and some of the strong solution and end up with 400 ml of a mild solution. Suppose that you take x ml of the weak solution then you know that you will need (400  x) ml of the strong solution since the the total amount must be 400 ml. You also know that the final solution is 40% acid, so in the final solution the amount of acid is 40% of 400 ml, that is
10% of the weak solution is acid, that is 10% of x ml is acid, so the amount of acid that comes from the weak solution is
50% of the weak solution is acid, that is 50% of (400  x) ml is acid, so the amount of acid that comes from the weak solution is
Since the total amount of acid is 160 ml you have
Solve for x. Cheers, 

