There are two barrels of oil, the first barrel is used (1/4), the second barrel is used 60%, the ratio of the remaining oil in the first barrel to the second barrel is 3:5, if the original oil in the second barrel 120 jins, how many jins of oil was originally contained in the first barrel.
有两桶油，第一桶用去(1/4)，第二桶用去60%，第一桶和第二桶内剩余油质量之比为3：5，若第二桶内原来装油120斤，求第一桶内原来装油多少斤．
<gadget id="calculator">60 / 100</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">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">120 * (2/5) * (3/5)</gadget>
<output>144/5 = around 28.8</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(144/5) / (3/4)</gadget>
<output>192/5 = around 38.4</output>

<result>192/5 = around 38.4</result>