Q = 180 ( 1.474) ^ t
This in in the form
y = a e ^ (kt)
180 is the initial value
a = 180
1.474 ^t = e^k ^ (t)
This means that e^k = 1.474
Taking the ln of each side
ln (e^k) = ln ( 1.474)
k = ln ( 1.474)
b = 1.474 which is the growth factor
b =1+r
1.474 = 1+r
r = .474
If they want r as a percent
r = 47.4 %