After increasing 100 kilograms by 30%, then reducing it by 30%, how many kilograms are left.
100千克增加它的30%后，再减少30%，剩下多少千克．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 + (3/10)</gadget>
<output>13/10 = around 1.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">100 * (13/10) * (7/10)</gadget>
<output>91</output>

<result>91</result>