Answer:
0.75m
Explanation:
The volume of a prism is:
the area of the cross section × length
In this case the cross section is the circle so the formula is
v = πr²h
volume = 21m³
height or length = 12m
Sub in the values:
21 = πr² × 12
1.75 = πr² (I divided both sides by 12)
0.5570423008 = r² (I divided both sides by π)
r = 0.74635... (I square rooted both sides)
r ≈ 0.75m (to 2 d.p)