Your answer is the second option, the volume becomes 27 times larger.
We can see this in two ways, either with an example, or by looking at what we're doing when we triple each side of a rectangular prism.
Firstly, if we were to say that each side was 1 unit, then the total volume of the prism would be 1 unit³. If we were to then triple each side, each side would be 3 units, and the volume would be 3 × 3 × 3 = 27 units³, and 27 is 27 times larger than 1.
If you want to understand why this happens, you just have to think that when you are finding the volume of a rectangular prism, you are multiplying together all sides. Therefore, if you multiply all of the sides by 3, you end up multiplying the total volume by 3, 3 times, and 3³ = 27.
I hope this helps!
