Adding till 100

Calculate:

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

54	+	31	=
24	+	14	=
25	+	60	=
21	+	28	=
52	+	40	=
4	+	6	=
5	+	5	=
53	+	47	=
23	+	21	=
35	+	30	=