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.
Improve 21x1=21 21x2=42 21x3=63 21x4=84 21x5=105 21x6=126 21x7=147 21x8=168 21x9=189 21x10=210
The multiples of 21 up to 500 are as follows: 21x1=21 21x2=42 21x3=63 21x4=84 21x5=105 21x6=126 21x7=147 21x8=168 21x9=189 21x10=210 21x11=231 21x12=252 21x13=273 21x14=294 21x15=315 21x16=336 21x17=357 21x18=378 21x19=399 21x20=420 21x21=441 21x22=462 21x23=483 21x24=504