The number of many one functions from A = {1, 2, 3} to B = {a, b, c, d} is

No of functions=43=64         {   n(B)n(A)  } No of one-one functions=P3   4=24       {   P ( n( B), n(A))   }No of many one functions (  =total functions - one one functions ) =   64-24 = 40