Question

Eric starts with 10 milligrams of a radioactive substance. The amount of the substance decreases by 12 each week for a number of weeks, w. He writes the expression 10(12)w to find the amount of radioactive substance remaining after w weeks. Andrea starts with 1 milligram of a radioactive substance. The amount of the substance decreases by 20% each week for a number of weeks, w. She writes the expression (1−0.2)w to find the amount of radioactive substance remaining after w weeks. Use the drop-down menus to explain what each part of Eric’s and Andrea’s expressions mean.

Answer 1

Andrea's Expression: (1 - 0.2)^w

w: number of weeks

0.2: percent decrease

1 - 0.2: decay factor for each week

I got Eric's Expression wrong :(