Final answer:
Sam and Glenn took approximately 2.33 hours to finish cleaning the pool.
Step-by-step explanation:
To find out how long it took Sam and Glenn to finish cleaning the pool when Sam cleaned it alone for an hour, we need to determine the rate at which they clean the pool together. Sam takes 5 hours to clean the pool, so his rate of work is 1/5 of the pool per hour. Glenn takes 7 hours to clean the pool, so his rate of work is 1/7 of the pool per hour. Working together, their combined rate of work is the sum of their individual rates: 1/5 + 1/7 = 7/35 + 5/35 = 12/35 of the pool per hour.
Since Sam worked alone for 1 hour, he completed 1/5 of the pool. So, the amount of work remaining for both of them to complete is 1 - 1/5 = 4/5 of the pool.
Now, we can use the combined rate to find out how long it takes them to finish the remaining 4/5 of the pool. Let's denote the time it takes as 't' hours. The equation to solve is: (12/35)t = 4/5.
Multiplying both sides of the equation by 35, we get: 12t = (4/5)35 = 28. Solving for 't', we find: t = 28/12 = 2.33 hours.
So, it took Sam and Glenn approximately 2.33 hours to finish cleaning the pool.