There is a bag of rice, 40% of it was eaten in the first week, 50% in the second week, and 3 kg more in the second week than in the first week. How many kilograms does this bag of rice originally weigh?
有一袋大米，第一周吃了40%，第二周吃了50%，第二周比第一周多吃了3千克．这袋大米原来有多少千克？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">3 / (1/10)</gadget>
<output>30</output>

<result>30</result>