Mike, an experienced bricklayer, can build a wall in 2 hours, while his son, who is Learning, can do the job in 6 hours. How long does it take for them to build a wall together? _ hours
[tex]\begin{gathered} \text{Mike can build a wall in 2 hour} \\ \text{His son can build a wall in 6 hour} \\ In\text{ one hour} \\ \text{Mike can build 1/2 of a wall} \\ \text{His son can build 1/6 of a wall} \\ \text{Hence} \\ \frac{1}{2}+\frac{1}{6}=\frac{2}{3} \\ In\text{ one hour they can build }\frac{2}{3}\text{ of a wall} \\ So \\ 1\text{ hour ----}\frac{2}{3}\text{ wall} \\ x\text{ ------- 1 wall} \\ \text{Solving x} \\ x=\frac{1\text{ wall}\cdot\text{ 1hour}}{\frac{2}{3}\text{ wall}} \\ x=\frac{3}{2}\text{hour} \\ \text{Therefore} \\ \text{They build one wall in }\frac{3}{2}\text{ of a hour} \end{gathered}[/tex]
