At the end of 1997, the amount of savings deposits in a bank reached 11.5 billion yuan, and it increased to 14.7 billion yuan at the end of 1998. What is the correct formula to calculate the increase by a few percent?
1997年末，某银行储蓄存款金额达115亿元，1998年末增加到147亿元，计算增长了百分之几的正确列式是多少
<gadget id="calculator">147 - 115</gadget>
<output>32</output>

<gadget id="calculator">32 / 115</gadget>
<output>32/115 = around 0.278261</output>

<result>32/115 = around 0.278261</result>