Use an oil gun to fill an empty fuel tank. The oil injected within 15 minutes accounts for 40% of the volume of the fuel tank. How many minutes will it take to fill the entire fuel tank?
用一支油枪往一只空油箱注油，15分内注入油占油箱容积的40%，再过几分钟才能注满整个油箱？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">15 / (2/5)</gadget>
<output>75/2 = around 37.5</output>

<gadget id="calculator">(75/2) - 15</gadget>
<output>45/2 = around 22.5</output>

<result>45/2 = around 22.5</result>