The mean monthly salary paid to 75 workers in a factory is Rs. 5680. The mean salary of 25 of m is Rs. 5400 and that of 30 ors is Rs. 5700. The mean salary of remaining workers is-

Required average
$$ = {\text{Rs}}{\text{.}}$$ $$\left[ {\frac{{\left( {5680 \times 75} \right) - \left\{ {\left( {5400 \times 25} \right) + \left( {5700 \times 30} \right)} \right\}}}{{75 - \left( {25 + 30} \right)}}} \right]$$
$$ = {\text{Rs}}{\text{. }}\left[ {\frac{{426000 - \left( {135000 + 171000} \right)}}{{20}}} \right]$$
$$\eqalign{ & = {\text{Rs}}{\text{. }}\left( {\frac{{120000}}{{20}}} \right) \cr & = {\text{ Rs}}{\text{. 6000}} \cr} $$