Why do we need double entry accounting system although we have single entry cash system?

simplest answer for that question is, double entry system provides us the better report & easy to understand.

we need double entry system eventough we have single entry system because double entry system can be accomodated in making of the financial report, its diffrence with single entry system is limited only recording just in the cash-in and cash-out .

in accounting system Dr is Cr and Cr is Dr either in cash only Dr debit and Cr is credit

 Double entry accounting provides detailed financial information for tracking financial performance and producing the income statement and net worth statement.