# Stock Solution Question

#### Dierdron

If I have a a 40% solution and a 95% solution, how much of each do I need to make a 70% solution with a final volume of 375 ml? My 30 credits in chemistry was too many years ago and I'm out of practice (and stuck.). I've been playing around with the stock formula and algebraically rearranging for some time. It's the constrained target volume twist that's stumping me.

Last edited:

#### Woody

Perhaps more of a maths question!

Simultaneous equations should do it:

Let x be the volume of the 40% solution
Let y be the volume of the 95% solution

The total volume required is 375ml so:
x+y = 375
also:
40*x+95*y = 70*375

two equations, two unknowns,
You ok from here?

#### Dierdron

Oh yeah, systems of equations. That’s much more efficient than the trial and error I used for the actual problem. This will come in handy for future dilutions. Thank you!

#### Dierdron

Worked out

Picture attached showes problem worked out

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