power systems

Geeze, here we go again with the "multiples of 11" ignorance....

"We" don't.

Maybe you do, but you would need to ask yourself that question then.

Search this forum, that same question has been asked and answered here at least twice that I can remember.

When you say "we" which country are you talking about? This may help to answer your question

"Eight eights are sixty four

Multiply by seven

When it's done, carry one,

and take away eleven.

Nine nines are eighty one

multiply by three

if it's more, carry four

and then it's time for tea."

[With apologies to the late A.A._Milne.]

If it do exist it may have originated in times gone by when counting was not that great. An additional one was added to ensure a fair deal.

refer to bakers dozen (12+1). 1 pound 1 shilling, etc.

220 volt was used to ensure 200 volt at the user.

In South Africa we even supply 240-250volt to make sure.