percent mixture problems

Question

How many gallons each of a 25% acid solution and 75% acid solution must be used to produce 100 gallons of a 75% acid solution?

Answer 1

the formula to solve this question is C1V1 + C2V2 = C3V3 where C = concentration, and V = Volume

 

let x = Volume of 75% solution, then 100g - x = V2

 

so 0.75x + 0.25(100g - x) = 100g x 0.65

 

0.75x + 25g - 0.25x = 65g

 

0.5x = 40g

 

x = 80g

So, we need 80g of 75% solution and 20g of 25% solution

 

Proof: 80 x .75 + 20 x .25 = 100 x .65; 60g + 5g = 65g