Prove or disprove that U(20) and U(24) are isomorphic.
By listing out the elements of U(20) = {1,3,7,9,11,13,17,19} and then their corresponding orders which are 1,4,4,2,2,4,4,2 and then the elements of U(24) = {1,5,7,11,13,17,19,23} and their corresponding orders which are 1,2,2,2,2,2,2,2 we can see that since the largest order of any element in these groups does not agree, then U(20) and U(24) cannot be isomorphic.
-Karen Morley
