Multiplication till 400

Calculate:

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

17	×	21	=
21	×	19	=
20	×	17	=
15	×	15	=
23	×	11	=
18	×	12	=
23	×	17	=
14	×	15	=
18	×	9	=
17	×	8	=