Introduction:
The Directive Principles of State Policy (DPSP) are guidelines given to the government of India to establish social and economic democracy by promoting the welfare of the people. These principles are not enforceable by any court, but the government is expected to use them as a guide while framing policies and legislation. The 42nd Amendment to the Indian Constitution, enacted in 1976, added several new principles to the DPSP.

Explanation:
The principle added to the DPSP by the 42nd Amendment was the participation of workers in the management of industries. This principle, also known as workers' participation in management, aims to ensure that workers have a say in the decision-making processes of the industries they work in. It recognizes the importance of the workers' perspective and their contribution to the success of the industry.

Importance of Workers' Participation in Management:
1. Enhances efficiency: Workers' participation in management can lead to better decision-making and increased efficiency. By involving workers in the decision-making process, their knowledge and experience can be utilized, leading to more effective and practical solutions.

2. Promotes industrial peace: When workers feel that their voices are heard and their interests are taken into account, it creates a sense of ownership and belongingness. This, in turn, promotes industrial peace and reduces conflicts between management and workers.

3. Improves quality of work life: Workers' participation in management can lead to a better quality of work life for employees. It allows them to have a say in matters that directly affect them, such as working conditions, safety measures, and welfare facilities. This can result in a more positive and conducive work environment.

4. Fosters innovation and creativity: Workers' participation in management encourages the sharing of ideas and suggestions. This can foster innovation and creativity as workers contribute their unique perspectives and insights. It can lead to the development of new and improved processes, products, and services.

5. Ensures social justice: The principle of workers' participation in management aligns with the broader goal of social justice. It recognizes the dignity and rights of workers and aims to create a more equitable and inclusive society. By giving workers a voice in decision-making, it helps to address power imbalances and promote a fairer distribution of benefits.

Conclusion:
The addition of the principle of workers' participation in management to the DPSP by the 42nd Amendment reflects the commitment of the Indian government to promote social and economic democracy. This principle recognizes the importance of workers in the industrial process and aims to give them a voice in shaping their own destinies. By involving workers in decision-making, it can lead to improved efficiency, industrial peace, and a better quality of work life.