Job task

After two hours and 40 minutes, the job is finished. Compared to last year, we were 40 minutes faster.
What is the percentage increase in our performance?

Correct answer:

p =  20 %

Step-by-step explanation:

$$\begin{gathered} a=2\cdot 60+40=160\text{min} \\ \Delta =40\text{min} \\ b=a+\Delta =160+40=200\text{min} \\ p=100\cdot \frac{\Delta }{b}=100\cdot \frac{40}{200}=\frac{100\cdot 40}{200}=\frac{4000}{200}=20\% \end{gathered}$$

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