1. The working day at the enterprise lasted 8 hours. During this time, the labor productivity was as planned for the first six hours, and then it decreased by $25 \%$. The director (in agreement with the labor collective) extended the shift by one hour. As a result, it turned out that again the first six hours were worked with planned productivity, and then it decreased by $30 \%$. By what percentage did the overall labor productivity for the shift increase as a result of extending the working day?
1. Answer: by 8 percent. Solution. Let's take 1 for the planned labor productivity (the volume of work performed per hour). Then before the shift extension, workers completed $6+1.5=7.5$ units of work per shift. And after the extension, $8+2.1=8.1$ units. Thus, the overall productivity per shift became $8.1: 7.5 \times 100 \% = 108 \%$ of the initial, meaning it increased by $8 \%$. Grading criteria. Correct solution - 7 points. Initial and final productivity per shift correctly expressed in conditional units, but the percentage ratio is expressed incorrectly - 4 points. In all other cases - 0 points.