How do we determine significant figures in calculations involving both addition/subtraction and multiplication/division?

One of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version. which property fits this description?

Ill give brainiestif one neutron initiates a fission event that produces two neutrons in the products, how many new reactions can now be initiated? if each of the neutrons produced in the first fission event then initiates a fission event that produces one neutron in the products, how many new reactions can now be initiated by each neutron? how many neutrons in total were produced by the two fission events described?

What is the percent by mass of oxygen in fe2o3