each filter removes 70% of the remaining impurities from the water. If you have 8 million particles of pollutant per gallon originally, how much pollution will you have after 3 passes through?

Answer 1

.3^3 = .09(.7) = ..063 x 8 x 10^6 = 0.504 x 10^6 = 504,000 particles per gallon left

remove 70% and 30% is left each of the 3 times

(1-.7)^2 = .3^2