Adding till 100

Calculate:

The number of examples:
Numerical difficulty:
Range of values:
Multiplicity:

27	+	33	=
21	+	31	=
37	+	61	=
40	+	46	=
25	+	55	=
31	+	39	=
14	+	22	=
37	+	42	=
19	+	19	=
27	+	29	=