Some "outputs" can only have one possible "input". These are useful to memorize.

4x4, 2 squares
3 + 1 2
7 + 3 4
3 - 4 1
2 × 1 2
3 × 1 3
6 × 2 3
8 × 2 4
12 × 3 4
3 ÷ 3 1
4 ÷ 4 1
4x4, 3 squares
6 × 1 2 3
24 × 2 3 4
5x5, 2 squares
3 + 1 2
9 + 4 5
4 - 1 5
2 × 1 2
3 × 1 3
5 × 1 5
6 × 2 3
8 × 2 4
10 × 2 5
12 × 3 4
15 × 3 5
20 × 4 5
3 ÷ 1 3
4 ÷ 1 4
5 ÷ 1 5
5x5, 3 squares
6 × 1 2 3
10 × 1 2 5
15 × 1 3 5
24 × 2 3 4
30 × 2 3 5
40 × 2 4 5
60 × 3 4 5
5x5, 4 squares
30 × 1 2 3 5
120 × 2 3 4 5

4x4, 2 squares
3 +	1 2
7 +	3 4
3 -	4 1
2 ×	1 2
3 ×	1 3
6 ×	2 3
8 ×	2 4
12 ×	3 4
3 ÷	3 1
4 ÷	4 1
4x4, 3 squares
6 ×	1 2 3
24 ×	2 3 4
5x5, 2 squares
3 +	1 2
9 +	4 5
4 -	1 5
2 ×	1 2
3 ×	1 3
5 ×	1 5
6 ×	2 3
8 ×	2 4
10 ×	2 5
12 ×	3 4
15 ×	3 5
20 ×	4 5
3 ÷	1 3
4 ÷	1 4
5 ÷	1 5
5x5, 3 squares
6 ×	1 2 3
10 ×	1 2 5
15 ×	1 3 5
24 ×	2 3 4
30 ×	2 3 5
40 ×	2 4 5
60 ×	3 4 5
5x5, 4 squares
30 ×	1 2 3 5
120 ×	2 3 4 5