A barrel of oil, 25% is used for the first time, 2.6kg is used for the second time, and 1.6kg is left. How much does this barrel of oil weigh in kg?
一桶油，第1次用去25%，第2次用去2.6kg，还剩下1.6kg．这桶油原重多少kg？
<gadget id="calculator">1.6 + 2.6</gadget>
<output>4.2</output>

<gadget id="calculator">25 / 100</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">4.2 / (3/4)</gadget>
<output>5.6</output>

<result>5.6</result>