Adding till 400

Calculate:

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

70	+	51	=
141	+	206	=
141	+	102	=
261	+	136	=
108	+	40	=
142	+	93	=
166	+	178	=
75	+	99	=
49	+	69	=
18	+	19	=