Question

fie x=abc+bca+cab un nr natural dem ca x este multiplu de 111

Answer 1

x=abc+bca+cab=100a+10b+c+100b+10c+a+100c+10a+b=
=111a+111b+111c=111(a+b+c)  deci x este multiplu de 111

Answer 2

x=a*100+b*10+c+b*100+c*10+a+c*100+a*10+b
x=111a+111b+111c
x=111*(a+b+c)
M111={1,111,222,333...}