标有"A","B","C","D","E"的小球各10个,至少有抽多少个球,才保证其中至少有两个字母相同的小球?

问题描述:

标有"A","B","C","D","E"的小球各10个,至少有抽多少个球,才保证其中至少有两个字母相同的小球?

6.至少.