On New Year's Day, six friends sat around a round table evenly to celebrate the festive season. The radius of the round table is 60cm, and the distance between each person and the round table is 10cm. Now there are two more guests, and each person moves back by the same distance, and then adjusts the position left and right so that everyone sits down. The distance is equal to the distance between the original 6 people (that is, the side of the arc between the two people on the circumference). How far did each move backward?
元旦那天，6位朋友均匀地围坐在圆桌旁共度佳节．圆桌的半径为60cm，每人离圆桌的距离均为10cm，现又来了两名客人，每人向后挪动了相同的距离，再左右调整位置，使每人都坐下，而且8人间的距离与原来6人间的距离(即在圆周上两人之间的圆弧的边)相等．每人向后移动了多少距离？
<gadget id="calculator">280 - 210</gadget>
<output>70</output>

<gadget id="calculator">70 / 3</gadget>
<output>70/3 = around 23.333333</output>

<result>70/3 = around 23.333333</result>