Question

Sibal started with $500 in a bank account that does not earn interest. In the middle of every month, she withdraws 1/5 of the account balance.   
Which recursive function rule models Sibal’s balance at the end of each month?

Answer 1

4/5 of the original amount at the start of the month will remain. The amount at the start of every month will change. Thus:
an = 4/5 (an-1) ; where a1 = 500.