To find the condition on \( p \) and \( q \) such that the minimum of \( Z = px + qy \) occurs at the points (3, 0) and (1, 1), we first calculate \( Z \) at these corners:
For (3, 0): \(Z = 3p + 0 \cdot q = 3p\)
For (1, 1): \(Z = 1 \cdot p + 1 \cdot q = p + q\)
To ensure the same minimum value at both points, we equate these expressions:
\[3p = p + q\]
Solving the equation for \( p \):
\[3p - p = q\]
\[2p = q\]
Thus, the condition required is:
\[p = \frac{q}{2}\]
This ensures that the minimum value of \( Z \) occurs at both (3, 0) and (1, 1).