20. 1491-!-item-!-187;#058&000755
A certain one-day seminar consisted of a morning session and an afternoon session. If each of the 128 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only?
(1) 3/4 of the people attended both sessions.
(2) 7/8of the people attended the afternoon session
這題答案為B..但是我選C
題目說128人中至少參加過早上或是下午session
代表128包括參加過早上,下午,以及兩場都參加的人
m+a+b(both)=128
m+7/8*128+3/4*128=128
求得m
請問各位我哪裡想錯了???