For every one potato in a sack, there are 2-5 seeds. The trick is to cut the nobby tuber so that each new chunk has at least one eye. This eye becomes a sprout, growing into a potato plant, sending out more roots, turning into more potatoes. If you are lucky (it's a good weather year, you hill them well, there is little pest/weed pressure, and you got a good variety) 1# of planted potato seed can yield 10# of new potatoes!
Last week the garden class helped to cut down about 85# of seed, to be planted today. I LOVE that the seed company sent our certified organic seed in a recycled box: would you like fries with that?!?