432 DS : each of 7 children has to hit at least 20 pitches. 求 the average pitch of the 7children 1 at least one child hit 0pitch 2 7childern as a whole hit 56 pitches 这道题我第一句话就没太懂,但是感觉1不能求出,所以选的B
题目是什么意思呢?搞不明白,照B说的 7childern as a whole hit 56 pitches ,那不是每个child hit less than 20 pitches了吗?~