For a group of saplings, if men and women are planted together, each person needs to plant 6 saplings on average. If only girls are allowed to plant, an average of 10 trees will be planted per person. If only boys are allowed to plant, how many trees are needed per person on average.
一批树苗，如果让男女一起栽，平均每人需栽6棵．如果只让女生栽，平均每人需栽10棵．若只让男生栽，平均每人需多少棵．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/6) - (1/10)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / (1/15)</gadget>
<output>15</output>

<result>15</result>