The school has planted 40 trees, among which pine trees account for (1/10), willow trees account for (2/5), poplar trees account for (3/8), and the remaining 5 trees are pagoda trees. Please design two math problems and try to solve them.
学校种了40棵树，其中松树占(1/10)，柳树占(2/5)，杨树占(3/8)，其余5棵是槐树，请设计两个数学问题，并尝试解答．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">40 * (2/5)</gadget>
<output>16</output>

<result>16</result>