Thank you for helping me in advace

Question

Recardo and Bisa have a new grandson. How much money should they invest now so that he will have $51,000 for his college education in 18 years? The money is invested at 5.1% compounded semiannually.

Answer 1

5.1% APR compounded semiannually is more than half, so take the square root of 1.051, raise it to the 36th power, and divide the final by that. $20,831.54 (rounded up)

Using half the interest rate as the 6 month rate, $20,600.91 (rounded up)