Sig figs chemistry chemistry math idk

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

28. which is not a reason that water is used to store spent fuel rods from nuclear power plants? water increases the speed of the chain reaction in the fuel rods. water protects nuclear power plant workers from the high temperature and radiation of the fuel rods. water acts as a radiation shield to reduce the radiation levels. water cools the spent rods. salts action

Find the missing probability in the table below a.0.10 b.40 c.0.80 d. 0.20