For exponential decrease use the formula P(1 - r)^t
p: initial amount
r: rate of change or percent of decrease (be sure to put in decimal form or you wont get the right answer)
t: amount of time (in years)
1,000,000 (1-0.042)^15 =
$525,391.01
(also make sure to use pemdas or order of operations when solving) hope this helps :)
