Adding till 100

Calculate:

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

40	+	51	=
16	+	8	=
41	+	50	=
27	+	43	=
12	+	14	=
37	+	49	=
16	+	13	=
43	+	31	=
23	+	36	=
3	+	12	=