1, 3, 9, 11, 33, 99
156
156
Try a factor tree. 99 33,3 11,3,3 3 x 3 x 11 = 99
1, 3, 11 and 33
99
1 + 3 + 9 + 11 + 33 + 99 = 156
1, 3, 9, 11, 33, 99.
1, 3, 9, 11, 33, 99
49 of them.
Use the formula for the sum of an arithmetic sequence. Start with 11, end with 99; the interval is 2.
The sum of all odd numbers 1 through 99 is 9,801.
All the common factors of 99 and 11 are: 1 and 11 .
All of them from 45 to 99 ... 55 integers.