Two solids are similar if their corresponding linear measurement units are proportional to each other. Scale factor is a/b, from the small prism, we get 8/10 or 4/5.
Congruent ratios will mean similar solids or in this case, prisms.
Set-up a proportion to find x.
4/5 = 4.8/x
4x = 34
x= 6 cm.
The height of the larger prism is 6cm.