Together 3

If Sally can paint a house in 4 hours, and John can paint the same house in 6 hours, how long will it take for both of them to paint the house together?

Correct answer:

t =  2.4 h

Step-by-step explanation:

$$\begin{gathered} t_1=4\text{h} \\ {t}_2=6\text{h} \\ {h}_1=1/t_1=1/4=\frac{1}{4}=0.25 \\ {h}_2=1/t_2=1/6=\frac{1}{6}\doteq 0.1667 \\ h=h_1+h_2=0.25+0.1667=\frac{5}{12}\doteq 0.4167 \\ t\cdot h=1 \\ t=\frac{1}{h}=\frac{1}{0.4167}=2.4\text{h} \end{gathered}$$

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