Answer:
3 hours
Step-by-step explanation:
This situation represents exponential decay which decays 25% every hour.
Rate of decay = r = 0.25
Initial amount = A = 64
Equation
y = a (1 - r) ^ t
where y is final amount = 27g
t is the time = to find
27 = 64(1 - 0.25)^t
27/64 = (1 - 0.25)^t
0.42 = (1 - 0.25)^t
Take log
ln(0.42) = ln(1 - 0.25)^t
ln(0.42) = (t) ln(1 - 0.25)
t = ln(0.42)/ln(1 - 0.25)
t = 3.015 hours
t ≈ 3 hours
