In china, the number of sport utility vehicle sold in 2003 was predicted to grow by 30% annually for the next 5 years. what is the doubling time?
when is
2 = 1 (1.3)^t
take ln of both sides
ln 2 = ln (1.3)^t
ln2 = t (ln 1.3)
t = ln 2/ln 1.3
= appr 2.64 yrs
or 2 years and 7.7 months
check
suppose there were 5 million sold now,
in 2.64 years, the number sold is
N = 5 (1.3)^2.64
= 9.995 million or double the original 5 million