what is the mathamatical formula to figure out how much concrete you will have left in your line at the end of a pour.  tomorrow i will have 200' of 4" line left out and the contractor asked what would be left. any help would be nice.

ConForm has a zippy chart that has all sort of that information on their web site.

300 FEET OF 4 INCH PLACING LINE CONTAINS ONE YARD OF CONCRETE THEREFORE 200 FEET CONTAINS A LITTLE BIT MORE THAN HALF YARD

thanks guys i almost had the answer but i brain farted when i had to convert cubic feet to cubic yards. boy it's been a while since i had to think about a math problem like this. once again thanks to everyone.

i just keep it simple 3 pipes to 1 wheel barrow

do the math on each section of line as per cubic foot of material. my ball pump 6x30 inch stroke was one half CF and two strokes would do apx 14 ft of 2.5 inch hose. my ST will have 3 CF left in the hopper pumped down and the 6x39 inch stroke is say 2.5 CF for two strokes which is about equal to the costom hoses that are 17, 18 and 19 ft. the goal is to shut of the truck mixer and push out the rest to finish the job and go into wash out, you have to do it every day to get the hang of it just like priming. 

Keep this chart handy on the back of a business card

you can get your weight of "concrete" if you know the per cubic weight of the mix.  look at the total weights of the mix, mixer ticket, divide by how many cubic yards he has on and then divide by 27

total weight 39,150  divided by 10 =3915 divided by 27 = 145 per cubic foot. 

If the 5 inch has  .052 cy in 10 feet and the concrete weighs 145lbs per cubic foot then you have

.052 (volume) x 145 (pcf) x 27 (cf/yard) = 203. 5 lbs    

hope this helps