After using up (3/5) of a barrel of lard, there is still 30 kilograms left in the barrel. How many kilograms does the barrel of lard originally weigh?
一桶猪油，用去(3/5)后，桶内还剩30千克，这桶猪油原来重多少千克？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">30 / (2/5)</gadget>
<output>75</output>

<result>75</result>