A store sells 840 kilograms of apples and 630 kilograms of pears in 7 days. On average, how many kilograms more apples are sold than pears per day?
某商店7天卖出苹果840千克，梨630千克，平均每天卖出的苹果比梨多多少千克？
<gadget id="calculator">840 / 7</gadget>
<output>120</output>

<gadget id="calculator">630 / 7</gadget>
<output>90</output>

<gadget id="calculator">120 - 90</gadget>
<output>30</output>

<result>30</result>