Answer:
[tex]133\text{ hours}[/tex]Explanation:
Since the pool is 2/3 full before opening the inlet and draining pipes, the wor to be done here is to fill 1/3 of the pool.
We simply need to calculate the time it takes to fill 1/3 of the pool
Let the time be x hours
While the inlet pipe will be postively adding, the draining pipe would be taking away
Mathematically,we have it that:
[tex]\begin{gathered} (\frac{1}{38}-\frac{1}{42})\times x\text{ = }\frac{1}{3} \\ \\ x(\frac{42-38}{38\times42})\text{ = }\frac{1}{3} \\ \\ \frac{12x}{1596}\text{ = 1} \\ \\ 12x\text{ = 1596} \\ x\text{ = }\frac{1596}{12} \\ \\ x\text{ =133 hours} \end{gathered}[/tex]