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 $3420. What is the average monthly balance maintained by John in his
account during the year?  Choose the correct answer:	A) 2840	B) 5680	C) 6840	D) 7540	E) 17100
Soln:-   Bank balance is doubled with accumulation of interest to 3420..   this means INTEREST is   3420/2= 
<gadget id="calculator">  3420/2</gadget>
<output>1_710</output>
1710 for entire year..   although since interest is 10% of avg MONthly balance, it becomes 17100..   ANSW17100R:17100
<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 $3420. What is the average monthly balance maintained by John in his
account during the year?