if you put them in piles of 5, then it could be:
30
35
40
45
50
but you have one left, so it could be then
31
36
41
46
51
if you put them in piles of 4 then it would be:
32
36
40
44
48
and if one is left then
33
37
41
45
49
and the only number both of those with one left in the ppile is 41!!
