GWD 18-20

[jerry7271]

查過了沒這題
Last year in a group of 30 businesses, 21 reported a net profit and 15 had investments in foreign markets. How many of the businesses did not report a net profit nor invest in foreign markets last year?
(1)Last year 12 of the 30 businesses reported a net profit and had investments in foreign markets.
(2)Last year 24 of the 30 businesses reported a net profit or invested in foreign markets, or both.

答案是D。 我是選A,不懂B為何也充分？ B不是說 or 以及 or both嗎？
怎麼會是充分呢

[吳]

Last year in a group of 30 businesses, 21 reported a net profit and 15 had investments in foreign markets. How many of the businesses did not report a net profit nor invest in foreign markets last year?
(1)Last year 12 of the 30 businesses reported a net profit and had investments in foreign markets.
(2)Last year 24 of the 30 businesses reported a net profit or invested in foreign markets, or both.

題目問非n非f
(2)n或f
30-n或f=非n非f=>30-24=6

[jerry7271]

題目問非n非f
(2)n或f
30-n或f=非n非f=>30-24=6[/quote]

其實我還是有點轉不過來，
(2)有說 24個 "有n或f "，但並不是"有n和f " 不是嗎？
要30-24的情況不是應該要 "n和f " 嗎？
最後出現的 or both ，是代表 " n和f "嗎？

亂亂亂.. 確定下禮拜要去考嗎

[sweetymanman]

Last year in a group of 30 businesses, 21 reported a net profit and 15 had investments in foreign markets. How many of the businesses did not report a net profit nor invest in foreign markets last year?
(1)Last year 12 of the 30 businesses reported a net profit and had investments in foreign markets.
(2)Last year 24 of the 30 businesses reported a net profit or invested in foreign markets, or both. 這裡的意思是求聯集

其實我還是有點轉不過來，
(2)有說 24個 "有n或f "，但並不是"有n和f " 不是嗎？
---所以p(n或f)=p(n)+p(f)-p(n和f)==>24=21+15-p(n和f), 故p(n和f)=12 可以畫圖看看喔
要30-24的情況不是應該要 "n和f " 嗎？
最後出現的 or both ，是代表 " n和f "嗎？

[scujean]

題目給a+b+c+d=30 ,a+b=21,a+c=15，可以確定21是a+b不是b。因為15+21>30(總人數)可見15和21理都有包含a
reported a net profit or invested in foreign markets, or both. ←這句話就是24=a+b+c，不可能是(a+b)+(a+c)+a因為(a+b)+(a+c)+a 至少大於36{=21 +15}

題目要求d/30

[jerry7271]

謝謝大家的回覆，我懂了，謝謝。