A bag of rice is 30 kilograms, 40% is eaten in the first week, and 50% is eaten in the second week, how many kilograms are left?
一袋米30千克，第一周吃了40%，第二周吃了50%，还剩多少千克？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

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

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

<result>3</result>