how to work this chem question?

[faerielynx]

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how many 10% acid solution should be mixed with 25% acid solution, to produce 3L of solution that is 15% acid?
a. 3L
b. 2L
c. 3.5L
d. 4L
e. 4.5L

 

[doc3232]

how many 10% acid solution should be mixed with 25% acid solution, to produce 3L of solution that is 15% acid?
a. 3L
b. 2L
c. 3.5L
d. 4L
e. 4.5L

Ok...so 15-10 is 5
and 25-10 is 15
this means we need 1 part 25% and 2 parts 10%. Hence, it is b.
I'm a bit tired so correct me if I am wrong.

 

[joonkimdds]

we want 3L. 3.5, 4, 4.5 are bigger than 3. 3+x should be bigger than 3 so the only possible answer is 2 cuz it's smaller than 3.
I actualy don't know how to solve this problem but I think it makes sense?

 

[klutzy1987]

This problem is actually a QR problem not a Gchem problem. The way you do it is to set up the equation
((X*.10)+(3-X)*.25)/3=.15
Solving gives .45=.1X-.25X+.75
This converts to -.3=-.15X
Solve for X gives us 2.