A bank pays interest to its customers on the last day of the year. The interest paid to a customer
is calculated as 10% of the average monthly balance maintained by the customer. John is a
customer at the bank. On the last day, when the interest was accumulated into his account, his
bank balance doubled to $5680. What is the average monthly balance maintained by John in his
account during the year?  Choices.
A) 2840
B) 5680
C) 6840
D) 7540
E) 28400
Soln:-   Bank balance is doubled with accumulation of interest to 5680..   this means INTEREST is   5680/2= 
<gadget id="calculator">  5680/2</gadget>
<output>2_840</output>
2840 for entire year..   although since interest is 10% of avg MONthly balance, it becomes 28400..   ANSW28400R:28400
<result>E</result>
A bank pays interest to its customers on the last day of the year. The interest paid to a customer
is calculated as 10% of the average monthly balance maintained by the customer. John is a
customer at the bank. On the last day, when the interest was accumulated into his account, his
bank balance doubled to $5680. What is the average monthly balance maintained by John in his
account during the year?