Question

Pedro deposited $7,350 into a savings account 21 years ago. The account has an interest rate of 4.5% and the balance is currently $18,810.67. How often does the interest compound?

Answer 1

The interest is compounded quarterly because the formula is
A=p (1+r/k)^kt
A it's 18810.67 but I will assume it's unknown ?
P present value 7350
R interest rate 0.045
K compounded quarterly 4
Now solve the formula as the interest is compoundedquarterly
A=7,350×(1+0.045÷4)^(4×21)
A=18,810.67

So the answer is quarterly