The school buys saplings to green the campus, each sapling is 20 yuan, buy 4 and get 1 free, and the school buys back 20 at a time, how much is it spent?
学校买树苗绿化校园，每棵树苗20元，买4棵送1棵，学校一次买回20棵，用去多少元钱？
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 * (4/5)</gadget>
<output>16</output>

<gadget id="calculator">16 * 20</gadget>
<output>320</output>

<result>320</result>