Return the greatest integer multiple of m less than or equal to n:
abjad> mathtools.greatest_multiple_less_equal(10, 47)
40
abjad> for m in range(1, 10):
... print m, mathtools.greatest_multiple_less_equal(m, 47)
...
1 47
2 46
3 45
4 44
5 45
6 42
7 42
8 40
9 45
abjad> for n in range(10, 100, 10):
... print mathtools.greatest_multiple_less_equal(7, n), n
...
7 10
14 20
28 30
35 40
49 50
56 60
70 70
77 80
84 90