Decoration

Jerry and Jane decided to decorate their common room. If Jerry painted it alone, it would take her 4 hours, and Jane 3 hours. How long would they paint the room if they painted together?

Final Answer:

s =  1.7143 h

Step-by-step explanation:

$$\begin{gathered} t_1=4\text{h} \\ {t}_2=3\text{h} \\ s\cdot (1/t_1+1/t_2)=1 \\ s\cdot f=1 \\ f=\frac{1}{t_1}+\frac{1}{t_2}=\frac{1}{4}+\frac{1}{3}=\frac{3}{12}+\frac{4}{12}=\frac{3+4}{12}=\frac{7}{12}\doteq 0.58331\text{/h} \\ s=\frac{1}{f}=\frac{1}{0.5833}=1.7143\text{h} \end{gathered}$$

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