On the Double Ninth Festival, the rice in Limin Supermarket is 3.4 yuan per kilogram, and my mother bought 6.4 kilograms. How much does my mother have to pay?
重阳节，利民超市的大米每千克3.4元，妈妈买了6.4千克，妈妈要付多少元？
<gadget id="calculator">3.4 * 6.4</gadget>
<output>21.76</output>

<result>21.76</result>