Posted by Anonymous on .
67.0 mL of a 1.50 M solution is diluted to a volume of 258 mL. A 129mL portion of that solution is diluted using 163 mL of water. What is the final concentration?

Chemistry 
DrBob222,
Assuming that the 129 mL plus the 163 mL added water adds to a total volume of 129+163. (That's the same thing as saying that I'm assuming the volumes are additive.
1.50 x (67.0 mL/258 mL) x [129 mL/(129+163)]