Simple Interest:
The formula for simple interest is: I = P * r * t, where I is the interest, P is the principle (initial investment), r is the interest rate, and t is the time in years.
For your investment of $9,000 at 7% interest for 40 years, the simple interest would be:
I = $9,000 * 0.07 * 40 = $25,200
So, the total amount after 40 years would be $9,000 + $25,200 = $34,200.
Compounded Quarterly:
The formula for compounded interest is: A = P * (1 + r/n)^(nt), where A is the total amount, P is the principle, r is the interest rate, n is the number of times compounded in a year, and t is the time in years.
For your investment of $9,000 at 7% interest compounded quarterly for 40 years, the total amount would be:
A = $9,000 * (1 + 0.07/4)^(4 * 40) = $70,598.74
Compounded Continuously:
The formula for continuously compounded interest is: A = P * e^(rt), where A is the total amount, P is the principle, r is the interest rate, and t is the time in years.
For your investment of $9,000