It looks like it is just minus nine each time.
The first number is 9 x 10, then 9 x 9, then 9 x 8.
as in the multiples? 9 18 27 36 45 54 63 72 81 90 99 ...
It is 83 because it is a prime number
77+72+90+70+81=390 390/5=78
54, 63, 72, 81, 90, 99.
They are: 54, 63, 72, 81, 90, 99.
72, 81, 90
72 out of 81 is 88.89%.
54, 63, 72, 81, 90, and 99 is.
9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99.
1,2,3,4,6,8,9,12,18,24,36,72 factor of 72 1,3,9,27,and 81 is factor of 81
18 27 36 45 54 63 72 81 90
9, 18, 27, 36, 45, 54, 63, 72, 81, 90