Answer:
It will take 250 seconds for 30 liters to pass through the pipe.
Explanation:
Let's use just the units only to help us set up and equation.
liters/sec × sec = liters
This works. Fill in the numbers we know.
.12 l/sec × ?sec = 30liters
Use a real variable and let's leave off the units so we can write an neater equation to solve.
.12 l/sec × x sec = 30liters
.12x = 30
That's a good equation. Divide by .12 to solve.
x = 30/.12
x = 250
Remember x was seconds. We were asked to find the seconds.
It will take 250 seconds for 30 liters to pass through the pipe.
(In case they ask later, that's 4minutes and 10 seconds)