If the average of m numbers is n² and that of n numbers is m² , then the average of (m + n) numbers is?

1. m – n
2. m + n
3. m/n
4. mn

Let’s analyze the problem:

• Average of m numbers = n²
• Average of n numbers = m²

Finding the total sum of all numbers:

• Total of m numbers = m * n²
• Total of n numbers = n * m²
• Total of (m + n) numbers = m * n² + n * m² = mn(m + n)

Finding the average of (m + n) numbers:

• Average = Total sum / Total numbers = mn(m + n) / (m + n) = mn

Therefore, the average of (m + n) numbers is mn.

So, the correct answer is (D) mn.