Two production teams, A and B, are making "Haibao" for the World Expo. Group A can do 200 per day, and group B can do 250 per day; group A can do 400 first, and then group B can do it. How many days did Group B do before they could do as much as Group A?
甲、乙两个生产组为迎世博做"海宝"．甲组每天可做200个，乙组每天可做250个；甲组先做了400个，乙组才开始做．乙组做了几天后，才能与甲组做的同样多？
<gadget id="calculator">250 - 200</gadget>
<output>50</output>

<gadget id="calculator">400 / 50</gadget>
<output>8</output>

<result>8</result>