The third and fourth grade students of a certain elementary school held a weekly waste paper collection activity. There were 35 students in the third grade, and a total of 420 kg of waste paper was collected. There were 45 students in the fourth grade, with an average of 14 kg per person. How much waste paper was collected in the third and fourth grades in a week? kilogram?
某小学三、四年级学生举行一周收废纸活动，三年级有35人，共收废纸420千克，四年级有45人，平均每人收集14千克，三、四年级一周共收废纸多少千克？
<gadget id="calculator">45 * 14</gadget>
<output>630</output>

<gadget id="calculator">420 + 630</gadget>
<output>1_050</output>

<result>1_050</result>