From the notebook
Volume of a Prism: Area of Cross-Section × Length
The rule for any prism is:
Volume = area of cross-section × length
If a prism has a triangular cross-section of area 18 cm² and length 12 cm, then:
Volume = 18 × 12 = 216 cm³
Why this helps
You do not need a different volume idea for every prism. The only part that changes is the way you find the cross-sectional area.
Final check: volume should always end in cubic units.
Useful next step: cover the worked answer and try the same method on a similar question before moving on.