A certain solution that is 30 percent acid is obtained by mixing x

­A certain solution that is 30 percent acid is obtained by mixing x gallons of a 20 percent acid solution with y gallons of a 60 percent acid solution, where the percents are according to volume. How many gallons of the 60 percent acid solution must be used to obtain 10 gallons of the 30 percent acid solution?

A. 0.75
B. 2.5
C. 3.3
D. 4.0
E. 5.0­

Here's the teeter-totter method: If you have 2 percentages of the additive solution and the final solution percentage, you set up up a line with with the two additive solutions with the final solution in the middle 20-----30------60, you find the difference to the final solution, 10 and 30, then reduce, 1:3, whichever is closest to the final solution (20) you give that the favor of the larger amount, so its 1:3 (1/4) 60 solution and 3:1(3/4) 20 solution, multiply 1/4 by 10 gallons to find the answer. 2.5

Hope that helps

­Use weighted avg formula to get ratio of 20% and 60% soln mixtures.

w1/w2 = 3/1

In 10 gallons 1/4th part is 2.5. Ans B

How are you guys getting the 1/4 * 10?

­its 1:3, the total is 4 parts, so its 1/4, if theres 2 parts in a ratio, lets say 1 part orange juice, 3 parts proseco, of the 4 parts, 1 part of the total 4 is orange juice,­