Following a severe snowstorm, ken and bettina reeves must clear their driveway and sidewalk. ken can clear the snow by himself in 3 hours, and bettina can clear the snow by herself in 5 hours. after bettina has been working for 1 hour comma kane is able to join her. how much longer will it take them working together to remove the rest of the snow?

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.