How the following can be calculated from ledger of a creditor. 1.Average Purchase Interval. 2.Avrg.Paymnt Interval. 3.Avrg.Invoice Paymnt in days.

1)  Average purchase interval

If the dates in a range are:

December2014,12th13th18th22nd and23rd

Then

[(2014/12/13 less2014/12) + (2014/12/18 less2014/12/13) ........ so on.....)]

divided by      4

thus:

= (1 DAY +5 DAY +4 DAY +1 DAY ) /4

=2.75 DAY

2)   Average payment interval:   

Total supplier purchases ---------------------------------------

[ (Beginning accounts payable + Ending accounts payable)] /2

3)   Average invoice payment in days

The Average Days to Pay =       (*Current  ADTP x Number of Paid Invoices) + Number of Days to Pay Invoice Just Paid __________________________________    Number of Paid Invoices +1        *The 'Current ADTP' is the last Average Days to Pay found in the ledger.