To calculate the interest that Mary will receive for the loan to Gerry after 6 months at an interest rate of 10 percent per year, we can use the formula for simple interest:
\[ \text{Interest} = \text{Principal} \times \text{Rate} \times \text{Time} \]
Where:
- Principal = $300
- Rate = 10% per year = 0.10 (as a decimal)
- Time = 6 months = 0.5 years
Now, substituting the values into the formula:
\[ \text{Interest} = 300 \times 0.10 \times 0.5 \]
\[ \text{Interest} = 300 \times 0.05 \]
\[ \text{Interest} = 15 \]
So, the interest that Mary will receive from Gerry after 6 months is $15.