One of these days, as I was revisiting my early high school memories from notebooks, books, love-letters etc, I stumbled upon this simple but also tricky problem:
“One pump can fill up a tank with petrol in 25 minutes.
Another tank can fill up the same tank with petrol in 15 minutes.
If we combine both pumps together, how much time is needed for the tank to be filled?”
You can try solving it on your own, before scrolling to the answer. Don’t spoil it so quickly!