People keep their surplus money in banks for safety and interest which is provided by banks to them. Banks again keep only a small proportion of their cash with themselves. These days banks keep only 15% of the total deposits with them. Rest of the money banks keep to extend loans. Banks charge interest on loans which is higher than the interest on deposits. This surplus interest becomes the source of income for the banks. The 15% of cash deposits which banks keep with themselves helps to carry on with, day-to-day transactions. Like everyday, depositors come to withdraw some of their cash