In a tube containing 1 ml of a 1:5 dilution of A, and 4 ml of a 1:100 dilution of B: What is the final dilution of substance A? What is the final dilution of substance B? Solution What is the final dilution of substance A? When 1mL substance A is mixed with 4 mL of Substance B, four dilution of substance A happens. original=1/5 Further =1/4 Final = 1/5 x1/4 = 1/20 fold dilution What is the final dilution of substance B? When 4mL substance B is mixed with 1 mL of Substance A, = times original=1/100 Further =4/5 Final = 1/100 x 4/5 = 4/500 fold dilution.