Question

Greg invested $9,000 in an investment account that earns 4.2% interest compounded monthly.

a) how much will he have in his account after 10
years?

b) how long will it take for this account to grow to
$15,400, rounded to the nearest tenth of a year?

Answer 1

Explanation:

`y=a(1+r/c)^(ct)\\ \\ y=9000(1+.042/12)^(12t)\\ \\ y=9000(1.0035)^(12t)\\ \\ a)\ y=9000(1.0035)^(12(10))=\$ 13687.61\\ \\ b)\ 15400=9000(1.0035)^(12t)\\ \\ 1.0035^(12t)=77/45\\ \\ 12t ln(1.0035)=ln(77/45)\\ \\ t=(ln(77/45))/(12ln(1.0035))\\ \\ t\approx 12.8\ years`