40
4, 9, 16, 25, and 36 are the square numbers between 1 and 40.
52
41 & 39 = 1599. (40 x 40 = 1600 but I assume you meant different numbers)
Not at all. For example: gcf(101, 102) = 1 gcf(40, 80) = 40
1,4,9,25,36
40
42
7 squared and 3 squared. 49 - 9 = 40
4, 9, 16, 25, and 36 are the square numbers between 1 and 40.
30 and 40
12 and 252 is a pair of numbers that fit those criteria.
8
20 and 40
20 and 20.
27 and 81 are a possibility. Also numbers like 5 and 10, 20 and 40.
52