Final answer:
The investor needs to purchase a minimum of 87 municipal bonds at $500 each to earn over $6,000 in interest, taking into account the $4,700 already earned from other investments and the 3% annual yield per bond.
Step-by-step explanation:
Minimum Number of Bonds to Earn Over $6,000 in Interest
To calculate the minimum number of municipal bonds the investor needs to purchase to earn over $6,000 in interest this year, we start by acknowledging the $4,700 interest already earned from other investments. The investor requires an additional $1,300 ($6,000 - $4,700) in interest to surpass the $6,000 mark.
As each municipal bond yields 3% annually, the interest per bond would be $500 × 0.03 = $15. To find the minimum number of bonds needed, we divide the additional required interest by the interest earned per bond: $1,300 / $15 = 86.67. Since the investor can't buy a fraction of a bond, they need to purchase a minimum of 87 bonds to exceed the $6,000 interest threshold.