How much money do I need now if I am going to receive $5000 every 6 months (starting in 6 months) for 10 years if the interest rates are 4%/a compounded semiannually?

To calculate the present value of receiving $5000 every 6 months for 10 years, we need to use the formula for the present value of an ordinary annuity.

The formula for the present value of an ordinary annuity is:

PV = PMT * (1 - (1 + r)^(-n)) / r

Where:
PV = Present value (the amount of money needed now)
PMT = Payment amount ($5000 every 6 months)
r = Interest rate per period (4% per year compounded semiannually, so 2% per 6-month period)
n = Number of periods (10 years, so 20 6-month periods)

Let's plug in the values and calculate:

PV = $5000 * (1 - (1 + 0.02)^(-20)) / 0.02

Now, we'll solve this equation step by step:

1 + 0.02 = 1.02
1.02^(-20) = 0.672673
1 - 0.672673 = 0.327327
0.327327 / 0.02 = 16.36635

Therefore, the present value (the amount of money you need now) is approximately $16,366.35.