教授, 請幫我看看這道題吧, 是不是題有問題呀? 謝謝先 :)

 Problem of the Week

In grade 11, science students can select a course in Physics, Biology or Chemistry. 18 selected Physics, 32 selected Biology, and 25 selected chemistry. Of these, 16 chose both Biology and Chemistry, but only 7 chose both Physics and Chemistry and only 8 selected both Physics and Biology. Just 3 selected to take all three courses. How many science students are there all together?

請您看看答案是  38, 還是 41

所有跟帖： 

• I used Venn Diagram to get 47. -BeLe- ♀ (0 bytes) () 02/12/2012 postreply 07:39:16

• 3個全選的算進去了嗎? -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 08:14:23

• Yes. You may want to google venn diagram. -BeLe- ♀ (96 bytes) () 02/12/2012 postreply 08:21:55

• 謝謝 -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 08:56:44

• 38 -pieq314- ♀ (0 bytes) () 02/12/2012 postreply 07:53:57

• 但是學Chemistry的隻有25個, 如果結果是38的話, 學chemistry的至少要26個, 所以, 我覺的這個題可能有問 -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 08:13:05

• 回複：教授, 請幫我看看這道題吧, 是不是題有問題呀? 謝謝先 :) -aChineseBostonian- ♂ (23 bytes) () 02/12/2012 postreply 08:00:55

• 3個全選的要減6嗎? -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 08:09:25

• 謝謝Pr總 -清清涼- ♀ (45 bytes) () 02/12/2012 postreply 08:51:38

• 謝謝泡泡 -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 08:49:16

• 47, 18+32+25-16-7-8+3=47. -jinjing- ♀ (0 bytes) () 02/12/2012 postreply 08:06:24

• 回複：47, (18+32+25)-9(?)-16-7-8+3=47. -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 08:10:15

• 術曰"加奇減偶".N(AUB)=N(A)+N(B)-N(AB),N(AUBUC)=N(A)+N(B)+N(C)-N(AB) -jinjing- ♀ (60 bytes) () 02/12/2012 postreply 08:26:18

• 謝謝 -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 09:01:01

• 我的解答 -aChineseBostonian- ♂ (80 bytes) () 02/12/2012 postreply 08:21:51

• 先從三個都選的開始(3個圓的交集)，那是3，然後...... -aChineseBostonian- ♂ (88 bytes) () 02/12/2012 postreply 08:29:31

• 有道理, 謝謝! 可能我理解錯了,我以為3個全選的不包括在選兩門課的人數中呢, -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 08:45:06

• 這樣的話你算出來比47還要大 -aChineseBostonian- ♂ (0 bytes) () 02/12/2012 postreply 08:50:53

• 我是用(18+32+25)-9-16-7-8+3算的, 覺的好象不對, 學化學的有點湊不起來, 你的解答對 -清清涼- ♀ (26 bytes) () 02/12/2012 postreply 08:56:19

• 謝謝大頭教授 -清清涼- ♀ (0 bytes) () 02/12/2012 postreply 08:48:47