http://images1f.snapfish.com/232323232fp934>nu=333:>23:>2;7>WSNRCG=323:76<89;698nu0mrj check on the link above , it is my workings on spreadsheet and data given . basic : i am being told , that two centrifugal pumps , diameter given , speed given , are pumping water , through two parallel pipes , to a tank , they want to know the difference of pipe flow and power between using 1 pump and 2 pumps . performance data and darcy f are given for the pumps , these are data to plot a H-Q and efficiency graph . what i did on the spreadsheet , is plotting the graph , get the parabolic curve equation , workout the A B C representing the properties of the pump , work out the x value , square it , then the number = pipe flow . so where do those other informations comes in ? i mean the dia , length , darcy f .