A barrel of oil has a net weight of 100 kilograms. After using up (1/10) of this barrel of oil, I buy another (1/10) of the oil in the barrel at this time. How many kilograms of oil are still in the barrel now?
一桶油净重100千克，用去这桶油的(1/10)以后，又买来这时桶里油的(1/10)，现在桶里还有多少千克的油．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">100 * (9/10)</gadget>
<output>90</output>

<gadget id="calculator">100 * (9/10) * (1/10)</gadget>
<output>9</output>

<gadget id="calculator">90 + 9</gadget>
<output>99</output>

<result>99</result>