Hi,

The exact question in the book is "Determine the number of homomorphisms from the additive group Z15 to the additive group Z10" (Zn is cyclic group of integers mod n under addition)

Now if the question asks to find the number of homomorphisms from Z15ontoZ10, then by the First Isomorphism Theorem I can prove that none exit. But if homomorphisms from Z15intoZ10 are allowed to be counted, how do I do it?