A barrel of oil is 40 kilograms, what is used is the rest (3/5), how many kilograms are used?
一桶油40千克，用去的是剩下的(3/5)，用去多少千克？
<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">40 * (3/8)</gadget>
<output>15</output>

<result>15</result>