ANS:A -

The logarithmic mean of two values, r1​ and r2​, is calculated using the formula: Logarithmic Mean=2−1ln⁡(2)−ln⁡(1)Logarithmic Mean=ln(r2​)−ln(r1​)r2​−r1​​ Where:

• r1​ and r2​ are the two values.

This formula is often used in heat transfer calculations, especially for determining the mean temperature difference in heat exchangers. So, if you have specific values for r1​ and r2​, you can use this formula to calculate the logarithmic mean. If you provide the values, I can assist you with the calculation.