Final concentrations unknown volume

[keen55]

Hi
I have a known volume of water with a known concentration of calcium.
I want to bring that volume up to a new (slightly) higher volume with a new (slightly) higher concentration. To do this I am adding a solution with a known concentration of Ca but cannot remember how to calculate the volume (of the second solution) I need to get to the final concentration. I cannot adjust the concentration of the second substance, I can only adjust the volume.
thanks

 

[mycotheology]

Use the equation: C1V1 = C2V2