a water main is 4 inches in diameter and is 320 feet long, you add 10lbs (65%) hth sodium hyprocloride what is the ppm (parts per million).

i know the first part is to figure out the gallons in the pipe which is 205.16 gal of water

.785x.33x.33.320x7.5=205.16 but iam having trouble going further.

i work in drinking water for a city and iam going for a state license and this question has me stumped thanks.