Two trucks, A and B, transport a batch of chemical fertilizers. In the first 4 days, the fertilizers transported by truck A accounted for (1/4) of this batch of fertilizers, and the truck B transported (1/6) of this batch of fertilizers was 20 tons more. The two trucks took another 5 days to finish transporting this batch of chemical fertilizers according to the original working efficiency. How many tons of this batch of chemical fertilizers are there?
甲、乙两车运一批化肥．前4天，甲车运的化肥正好占这批化肥的(1/4)，乙车运的是这批化肥的(1/6)还多20吨．两车按原来的工作效率又用了5天将这批化肥恰好运完，这批化肥共有多少吨？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

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

<gadget id="calculator">(1/4) / 4</gadget>
<output>1/16 = around 0.0625</output>

<gadget id="calculator">(1/9) - (1/16)</gadget>
<output>7/144 = around 0.048611</output>

<gadget id="calculator">(7/144) * 4</gadget>
<output>7/36 = around 0.194444</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(7/36) - (1/6)</gadget>
<output>1/36 = around 0.027778</output>

<gadget id="calculator">20 / (1/36)</gadget>
<output>720</output>

<result>720</result>