Consulting your 4th-grade times tables, you know Samuel took 5*9 = 45 liters of water to the game.
In case you forgot that math fact, you can use a calculator to reproduce it.
In case you forgot that multiplication simplifies repeated addition, you can simply add up the numbers.
.. (9 L) +(9 L) +(9 L) +(9 L) +(9 L) = 45 L
