Workers plant a batch of electric poles, 12 poles per day, which can be completed in 30 days. If it is required to be completed in 24 days, how many poles will be planted on average per day?
工人栽一批电杆，每天栽12根，30天可以完成，如果要求24天完成，平均每天要栽多少根？
<gadget id="calculator">12 / 24</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 * (1/2)</gadget>
<output>15</output>

<result>15</result>