Question

$1 is invested into an account that has a APR of 8% compounded quarterly. How long will it take for my money to double? To triple?

Answer 1

for doubling

1(1.02)^n = 2 , where n is in quarter years..
take log of both sides

log (1.02)^n = log2
n log 1.02 = log 2
n = log 2/log 1.02 = appr 35 quarters
or 8.75 years

you try the tripling part.