Construction work

A group of masons had to finish the rough construction within three days. On the first day, they completed a third of this task, but on the second day, they were delayed and did 15% less work than the first day. By what % relative to the second day must they increase their performance on the third day to complete the building?

Final Answer:

p =  35.29 %

Step-by-step explanation:

$$\begin{gathered} r_1=100\%-15\%=1-\frac{15}{100}=0.85 \\ a=\frac{1}{3}\doteq 0.3333 \\ b=a\cdot r_1=\frac{1}{3}\cdot \frac{17}{20}=\frac{1\cdot 17}{3\cdot 20}=\frac{17}{60}\doteq 0.2833 \\ a+b+b\cdot x=1 \\ 0.33333333333333+0.28333333333333+0.28333333333333\cdot x=1 \\ 0.283333x=0.383333 \\ x=\frac{0.38333333}{0.28333333}=1.35294118 \\ x=\frac{23}{17}\doteq 1.352941 \\ p=100\cdot (x-1)=100\cdot (1.3529-1)=\frac{600}{17}\%=35.29\% \end{gathered}$$

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