The store sold 600 repeaters in the first half of the year and 840 repeaters in the second half. The average number of repeaters sold per month throughout the year.
商店上半年卖出复读机600台，下半年卖出复读机840台．全年平均每月卖出复读机多少台．
<gadget id="calculator">600 + 840</gadget>
<output>1_440</output>

<gadget id="calculator">1_440 / 12</gadget>
<output>120</output>

<result>120</result>