Step by step
The question
Question: find the volume of a triangular prism with triangle base 6 cm and height 2 cm, and length 5 cm.
1 Area of the base
A prism has the same shape all the way through.
Here it is a triangle.
The triangle is the base.
Careful: the prism lies on its side.
Its base is the triangle at the end, not the face it lies on.
The triangle is half of the box around it.
So its area is half of base times height: A = ½ × 6 × 2.
6 times 2 is 12.
That is the whole box.
Half of 12 means 12 divided by 2.
That is 6.
So the base is A = 6 cm².
2 Base times length
The prism is that triangle, stacked up 5 cm long.
So the volume is V = A × length.
Now put the numbers in: A = 6 and length = 5.
6 times 5 is 30.
We count cubes, so the unit is cm³.
So the volume is 30 cm³.
Let's look back.
First: area of the base.
Last: base times length.