Question

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

Answer 1

Answer:

Step-by-step explanation:

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