Let's denote the average salary of the 25 engineers as \( x \) rupees. Therefore, the total salary of the engineers is \( 25x \).
We are given that the average salary of all 30 employees (both managers and engineers) is 60000 rupees. Thus, the total salary of all employees is:
\[ 30 \times 60000 = 1800000 \text{ rupees} \]
The total salary of the managers is a part of this total. Let's denote the original average salary of the 5 managers as \( y \). Thus their total original salary is:
\[ 5y \]
Therefore, the equation representing the sum of the salaries for the managers and engineers is:
\[ 5y + 25x = 1800000 \]
After a 20% increase in the manager's salary, each manager gets \( 1.2y \). Thus, their total new salary becomes:
\[ 5 \times 1.2y = 6y \]
The new average salary of all employees increases by 5%, making the new total salary:
\[ 1800000 \times 1.05 = 1890000 \text{ rupees} \]
The new equation, after the salary increment, is:
\[ 6y + 25x = 1890000 \]
We now have two equations:
\[ \begin{align*} 5y + 25x &= 1800000 \\ 6y + 25x &= 1890000 \end{align*} \]
Subtract the first equation from the second:
\[ (6y + 25x) - (5y + 25x) = 1890000 - 1800000 \]
Leading to:
\[ y = 90000 \]
Substitute \( y = 90000 \) back into the first equation:
\[ 5 \times 90000 + 25x = 1800000 \]
Solving that gives:
\[ 450000 + 25x = 1800000 \]
\[ 25x = 1800000 - 450000 = 1350000 \]
\[ x = \frac{1350000}{25} = 54000 \]
Therefore, the average salary of the engineers is \(\boxed{54000}\) rupees.
For any natural number $k$, let $a_k = 3^k$. The smallest natural number $m$ for which \[ (a_1)^1 \times (a_2)^2 \times \dots \times (a_{20})^{20} \;<\; a_{21} \times a_{22} \times \dots \times a_{20+m} \] is: