The happy primary school life is coming to an end. The four students in Class 6 and Class 2 agreed to water the saplings of their alma mater during the summer vacation. The number of trees watered by the first student is half of the total number of trees watered by other students, and the number of trees watered by the second student is (1/3) of the total number of trees watered by other students, the number of trees watered by the third student is (1/4) of the total number of trees watered by other students, and the fourth student just watered 13 trees. How many trees to water?
愉快的小学生活就要结束了，六2班四位同学约定暑假期间给母校树苗浇水，第一位同学浇树棵数是其他同学浇树总数的一半，第二位同学浇树棵数是其他同学浇树总数的(1/3)，第三位同学浇树棵数是其他同学浇树总数的(1/4)，而第四位同学刚好浇树13棵，四位同学共负责给多少棵树浇水？
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

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

<gadget id="calculator">1 + 4</gadget>
<output>5</output>

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

<gadget id="calculator">1 - (1/3) - (1/4) - (1/5)</gadget>
<output>13/60 = around 0.216667</output>

<gadget id="calculator">13 / (13/60)</gadget>
<output>60</output>

<result>60</result>