Its due tomorrow answer as fast as u can

Why does his teacher ask him to balance the equation by including the correct coefficient

3.09 lab: reaction of metals 1 which combinations of substances resulted in a chemical change? for each metal that participated in a chemical change, write the type of metal it is, based on your examination of the periodic table. were there any metallic compounds that did not react with either the acid or the base? write the type of metal, based on your examination of the periodic table. make a general statement about the reactivity of the metals in this experiment.

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