Xiao Ming deposits 1,000 yuan in the bank for a whole year, and donates the after-tax interest to the disaster area after maturity. If the annual interest rate is 2.25%, the deposit interest will be taxed at a rate of 20%. After maturity, Xiao Ming can donate to How much is the disaster area?
小明把1000元存入银行，整存整去一年，到期后把税后利息捐赠给灾区，如果年利率为2.25%，存款利息要按20%的税率纳税，到期后小明可以捐赠给灾区多少元．
<gadget id="calculator">2.25 / 100</gadget>
<output>0.0225</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1_000 * 0.0225 * 1 * (4/5)</gadget>
<output>18</output>

<result>18</result>