Oliver's grandfather invested $150 at 5% interest compounded quarterly. When Oliver inherited it, the amount was $6000. For how many years had the $150 been invested?
0.05/4=1.25% quarterly interest 6000=150(1+0.0125)^n , n= number of quarters (1+0.0125)^n=6000/150=40 n log (1.0125)=log 40 n=296.95 quarters number of years=n/4=74.23 years.
