An element with a mass of 700 grams decays by 6.1% per minute. To the nearesttenth of a minute, how long will it be until there are 220 grams of the element remaining?
220 = 700 x (0.939)^m
220/700 = (0.939)^m
m = Log(220/700) / Log(0.939)
m =18.4 minutes
