Xiaohong's mother deposited all of Xiaohong's New Year's money in the bank after the Spring Festival. Calculated at an annual interest rate of 5.5%, the interest she can get after one year is exactly 99 yuan. So how much is the principal that her mother deposited for Xiaohong?
小红妈妈春节后把小红的压岁钱全部存入银行，按年利率5.5%计算，一年后可得利息正好是99元，那么妈妈帮小红存入的本金是多少元．
<gadget id="calculator">5.5 / 100</gadget>
<output>0.055</output>

<gadget id="calculator">99 / 0.055</gadget>
<output>1_800</output>

<result>1_800</result>