Question 81510
There would be {{{0.05a}}} left if the initial amount was {{{a}}} after {{{x}}} years.
0.05a = a(0.5)^x
0.05 = (0.5)^x
log(0.05) = x * log(0.5)
log(0.05) / log(0.5) = x
x = about 4.32
4.32... * 30 = 129.65784 years