If a company has three bank accounts for processing payments, what is the minimum number of ledgers it needs?

You can create one mother bank a/c in chart of accounts and the3 bank accounts as sub account this way1 ledger is good to reconcile, simple and clean.

Also, if the volume of payments is high i suggest to keep different ledgers from the point of view for clean audit.

Only one ledger is needed but you would use three journals.  In todays world you would simply have three separate accounts in your chart of accounts.

You must keep 3 ledger accounts in the name of the 3 banks, then only you can easily reconcile it. I worked with a firm which have 6 bank accounts in Bahrain. I was keeping 6 ledger accounts.

Use this as a starting point to explore a candidate’s knowledge of ledgers. Observe the candidate’s initial reaction and use it as a leaping off point for further discussion of skills related to the opening you are trying to fill. Expect the candidate’s response to reveal the extent to which she has thought through how accounts relate to lines of business and generally accepted accounting principles.

The Question asked is "

hence the minimum number required is 1.

whether you keep 3 different accounts or 1 master account

I think no matter how many credit accounts in banksmatter how many credit accounts, the company needs only to Ostagil transactions by one book no