For a pile of chemical fertilizers, all (1/5) of the fertilizer is used on the first day, 2.3 tons are used on the second day, and 2.5 tons are used on the third day, and the whole weight (4/15) is left. How many tons of fertilizer are left ?
一堆化肥，第一天用去全部的(1/5)，第二天用去2.3吨，第三天用去了2.5吨，还剩全部重量的(4/15)，问剩余化肥多少吨？
<gadget id="calculator">2.3 + 2.5</gadget>
<output>4.8</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4 / 15</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">1 - (1/5) - (4/15)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">4.8 / (8/15)</gadget>
<output>9</output>

<gadget id="calculator">9 * (4/15)</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>