Answer: $22,643
Explanation:
To calculate how much Tim's grandparents need to invest in the account now, we can use the formula for compound interest:
A = P(1 + r/n)^(nt)
Where:
A is the future value of the account (which is $50,000 in this case),
P is the principal amount (the initial investment we want to find),
r is the annual interest rate (6% in this case),
n is the number of times the interest is compounded per year (twice a year, so n = 2),
and t is the number of years (18 years in this case).
Let's plug in the given values and solve for P:
$50,000 = P(1 + 0.06/2)^(2 * 18)
Simplifying the equation further:
$50,000 = P(1 + 0.03)^(36)
$50,000 = P(1.03)^36
To find the value of P, divide both sides of the equation by (1.03)^36:
P = $50,000 / (1.03)^36
Using a calculator, we find that (1.03)^36 is approximately 2.2049.
P = $50,000 / 2.2049
P ≈ $22,643
Therefore, Tim's grandparents need to invest approximately $22,643 in the account now to achieve a future value of $50,000 over 18 years with a 6% annual interest rate compounded semi-annually.