The grain store brings in 20 bags of rice and 20 bags of flour, each bag of rice is 45 kg, and each bag of flour is 25 kg.
粮店运进大米和面粉各20袋，每袋大米45千克，每袋面粉25千克，运进的大米比面粉一共多多少千克．
<gadget id="calculator">20 * 45</gadget>
<output>900</output>

<gadget id="calculator">20 * 25</gadget>
<output>500</output>

<gadget id="calculator">900 - 500</gadget>
<output>400</output>

<result>400</result>