In order to prevent pests and diseases, it is necessary to brush lime water on 50 small trees. If the average diameter of each tree is 5m, and each tree is 0.5m long, 0.4kg of lime water is needed per square meter, how many kilograms of lime water are needed in total? (retain one decimal place)
为了防治病虫害，需要给50棵小树刷石灰水．如果平均每棵树的直径是5m，每棵刷0.5米，每平方米需石灰水0.4kg，一共需石灰水多少千克？(得数保留一位小数)
<gadget id="calculator">3.14 * 5 * 0.5 * 50 * 0.4</gadget>
<output>157</output>

<result>157</result>