The formula to calculate the average rate (AVR) is:
\[ AVR = \frac{IR + FR}{2} \]
Where:
Let's say the initial rate is 10, and the final rate is 20. Using the formula:
\[ AVR = \frac{10 + 20}{2} \]
We get:
\[ AVR = 15 \]
So, the average rate (\( AVR \)) is 15.