Jake forgot to replace the cap on a bottle of cologne. the cologne began to evaporate at the rate of 18% per day. if the original amount of cologne in the bottle was 50 grams, which of the following graphs best represents the amount of cologne f(x) remaining in the bottle after x days?

y = 50(1-0.18)ˣ, or y = 50(0.82)ˣ

explanation:

this can be represented as an exponential growth equation,

y = a(1+r)ˣ, where a is the original amount, r is the rate of increase (or decrease) and x is the amount of time.

for this problem, a = 50 since it is the original amount of cologne.   the cologne decreases by 18% each day; r = 18% = 18/100 = 0.18; since it is decreasing, r = -0.18:

y = 50(1+-0.18)ˣ

combining the numbers in parentheses gives us

y = 50(0.82)ˣ