The banknote counter counts 900 banknotes in 1 minute, and the banknote counter counts 870 banknotes in 3 minutes. How many banknotes per minute are the banknote counters less than the banknote counters?
点钞机1分钟点900张钞票，点钞员3分钟点了870张钞票，点钞员每分钟比点钞机少点多少张钞票？
<gadget id="calculator">870 / 3</gadget>
<output>290</output>

<gadget id="calculator">900 - 290</gadget>
<output>610</output>

<result>610</result>