Question

Calculate the missing length for this cylinder

Answer 1

For first cylinder Vloume = pi * r^2 * h 
where h is the height and r is the radius 
so by substitute
6908=pi * r^2 * 22
so r = 9.99 cm
For second cylinder Vloume = pi * r^2 * h 
by substitute  
7884.54 = pi * r^2 * 31
so r = 8.99 
but the diameter is the required so 
d= 2*r = 2*8.99 
d= 17.99 cm

Answer 2

I assume by the length you mean height so,

$\frac{6908}{ \pi * 22^{2} }$ ≈ 4.54.

if you're supposed to round it, it'd be either 4.50, or 5

I hope this helps