How might you modify the popcorn experiment to find out whether the presence of duds did or did not make a difference in my calculations

Categorize them by metal, nonmetal, in periodic tableductilenon-ductilemalleableoften gain electrons easilygood conductorpoor conductorcan be liquidselements

Which of the following reactions represents an exothermic reaction? nh3(g) + 12.0 kcal ½n2(g) + 3/2 h2(g) ch4 + 2o2 co2 + 2h2o + 212,800 cal c + 2s cs2, h = 27,550 cal c(graphite) c(diamond), h = 0.45 kcal 2h2o 2h2 + o2, h = +58 kcal

Why does 4.03/0.0000035 = 1.2 x 106, instead of a different number of significant figures?