Rice is 3.2 yuan per kilogram. Dad bought 25 kilograms of rice and paid 100 yuan. How much money did he get back?
大米每千克3.2元，爸爸买了25千克大米，付出100元，找回多少钱？
<gadget id="calculator">3.2 * 25</gadget>
<output>80</output>

<gadget id="calculator">100 - 80</gadget>
<output>20</output>

<result>20</result>