A barrel of oil weighs 100kg. After using up (1/10) of this barrel of oil, you buy and use (1/10) again. How many kilograms of oil are in the barrel at this time?
一桶油重100kg，用去这桶油的(1/10)以后，又买来用去的(1/10)，这时桶里有油多少kg？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

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

<gadget id="calculator">100 - 10</gadget>
<output>90</output>

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

<gadget id="calculator">90 + 1</gadget>
<output>91</output>

<result>91</result>