Incorrect Use the equation for work, $\displaystyle{r}=\frac{{W}}{{t}}\usepackage{cmbright}\Huge\$ , to figure out how to represent the pipes. Since the rate of the fast pipe is $\displaystyle\frac{{1}}{{p}}\usepackage{cmbright}\Huge\$ (because it fills 1 pool in p hours), the rate of the slow pipe is $\displaystyle\frac{{1}}{{{2}{p}}}\usepackage{cmbright}\Huge\$ (because it takes twice as long for the slow pipe to do the same amount of work). It takes both pipes 5 hours to fill 1 pool, so write $\displaystyle\frac{{1}}{{p}}+\frac{{1}}{{{2}{p}}}=\frac{{1}}{{5}}\usepackage{cmbright}\Huge\$ . Now solve for p.