There are infinitely many multiples of 9 and it is not possible to add them all.
10. They are the first ten multiples of 9.
That the sum of its digits add up to 9 as for example 9*9 = 81 and 8+1 = 9
They are the first three multiples of LCM(5, 9), that is, the first three multiples of 45.
The first 5 multiples of 9 are: 9, 18, 27, 36, and 45.
The first 6 multiples of 9 are 9, 18, 27, 36, 45 and 54. Their sum (total) is 189. In other words, 1x9 + 2x9 + 3x9 + 4x9 + 5x9 + 6x9 = 21x9 = 189.
The sum of the first 10 multiples of 3 is 165.
There are infinitely many multiples of 9 and it is not possible to add them all.
10. They are the first ten multiples of 9.
.....5 .....Σ 9r ...r=1
9, 18 27 36 45 54 63 72 81 90
That the sum of its digits add up to 9 as for example 9*9 = 81 and 8+1 = 9
The sum of the first 25 numbers is 25*26/2 = 325 So the sum of the first 25 multiples of 12 is 325*12 = 3900
Sum of the first 15 positive integers is 15*(15+1)/2 = 120 Sum of the first 15 multiples of 8 is 8*120 = 960
The first three multiples of 3 are 3, 6, 9 The first three multiples of 9 are 9, 18, 27 As the lowest common multiples of 3 and 9 is 9, the common multiples of 3 and 9 are the multiples of 9, thus: The first three common multiples of 3 and 9 are 9, 18, 27
The digital sum of multiples of 9 always add up to 9 as for example 9*9 = 81 and 8+1 = 9
The sum of the digits is also a multiple of 9. And, if the sum of the digits is too large, you can sum those digits and keep going.