Question

Demarco starts with 10 milligrams of a radioactive substance. The amount of the substance decreases by 40% each week for a number of weeks, w. The expression 10(1 – 0.4)w finds the amount of radioactive substance remaining after w weeks. Which statement about this expression is true?

Answer 1

c It is the product of the initial amount and the decay factor after w weeks

Explanation:

Answer 2

Explanation:

Given that Demarco starts with 10 mg of a radioactive substance. The decay is given by 40% of available substance.

i.e. P = P0 = 10 mg in the beginning

After 1 week this would be 6 mg = 10(1-0.4)

After 2 weeks this would be 6(1-0.4) = 10(1-0.4)^2

Continuing like this we have

after w weeks the available substance

P(w) = 10(1-0.4)^2

i.e. It is the product of initial amount 10 and the 0,6 raised to power w.