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 $6840. What is the average monthly balance maintained by John in his
account during the year?	Select: A) 2840 B) 5680 C) 6840 D) 7540 E) 34200
Soln:-   Bank balance is doubled with accumulation of interest to 6840..   this means INTEREST is   6840/2= 
<gadget id="calculator">  6840/2</gadget>
<output>3_420</output>
3420 for entire year..   although since interest is 10% of avg MONthly balance, it becomes 34200..   ANSW34200R:34200
<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 $6840. What is the average monthly balance maintained by John in his
account during the year?