Adding till 400

Calculate:

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

21	+	28	=
225	+	133	=
72	+	51	=
121	+	186	=
177	+	72	=
103	+	170	=
146	+	170	=
73	+	47	=
202	+	173	=
167	+	151	=