Explanation:
consider the cylinder standing upright.
we have to assume that 20.4 cm is the diameter of the circle.
it is not clear what dimension of the result is needed : cm³ or m³, cm² or m². it is important that we do our calculations always with the same dimension of all operands (don't mix apples and oranges in the same calculation).
the volume of such a cylinder (or any regular 3D object) is
base area × height
for a cylinder the base area is a circle :
pi × r²
r being the radius (half of the diameter).
so, we have
r = 20.4/2 = 10.2 cm
height = 22 m = 2,200 cm (1 m = 100 cm)
volume = pi × (10.2)² × 2200 =
= 719,072.8593... cm³ =
= 0.7190728593... m³
≈ 719,072.86 cm³
≈ 0.72 m³
for the surface of a cylinder we need to imagine to cut the cylinder open with straight cut from the top to the bottom and then put the result flat on the table.
this result is a rectangle.
length = height of the original cylinder.
width = circumference of the original cylinder (and its circular base) = 2 × pi × r
the surface area of the cylinder is then
2 × base circle area (top and bottom) = 2 × pi × r²
plus
the area of that rectangle
length × width = height × 2 × pi × r
that is
height×2×pi×r + 2×pi×r² = 2×pi×r×(height + r)
in our case now
surface area = 2×pi×10.2×(2200 + 10.2) =
= pi×20.4×2210.2 =
= 141,648.3809... cm² =
= 14.16483809... m²
≈ 141,648.38 cm²
≈ 14.16 m²
remember, because
1 m = 100 cm
then
1 m² = 1 m × 1 m = 100 cm × 100 cm = 10,000 cm²
1 m³ = 1 m × 1 m × 1 m = 100 cm × 100 cm × 100 cm =
= 1,000,000 cm³