One Day 20 Questions

And Then One Day: A Memoir is an autobiography of

One day is equal to

A radioactive sample is decayed 20% in one day. After next two days, the undecayed percentage of nuclei will be

If 20 persons can clean 20 floors in 20 days, then in how many days can 16 persons clean 16 floors?

If A's one day's work is (3)/(20) , then A can finish the whole work in ……… days.