PP-T1-DS-20

[pauline_chiou]

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???

[Huang Hsin-Yi]

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
建議你觀念要再看一下og144
m+a+b(both)=128
(m-both)+both+(a-both)=128
m+7/8*128+3/4*128=128
求得m

請問各位我哪裡想錯了???

[pauline_chiou]

謝謝~~Huang Hsin-Yi

所以說

(2)(m-both)+(a-both)+b=128
可以得m+a-b=128
又條件(2) 7/8of the people attended the afternoon session=7/8*128+b(有包含m,a都參加)
代入公式
可得m+112+b-b=128,可得m=16
是這樣解嗎??

[Huang Hsin-Yi]

答對了

[pauline_chiou]

謝謝~~~^^
快打結了@@

[Philosophia]

謝謝~~Huang Hsin-Yi

所以說

(2)(m-both)+(a-both)+b=128
可以得m+a-b=128
又條件(2) 7/8of the people attended the afternoon session=7/8*128+b(有包含m,a都參加)

代入公式
可得m+112+b-b=128,可得m=16
是這樣解嗎??

請問為什麼是7/8*128 + both
若 a 所代表的是只參加下午場的人，那為什麼不是 a = 7/8*128 - both

另請問Huang Hsin-Yi 所提到的OG 144，我好像找不到相對題型...

[Philosophia]

哎呀~終於釐清了，我的盲點出現在未知數的定義上～

[Huang Hsin-Yi]

Cong!