How to answer this question in the easiest way.

joyxiang007 · 发表于 2013-11-22 12:20:09

In a certainclass,10students can play the piano,14students can play the violin,11studentscan play the flute.If 3students can play exactly three instruments,20 studentscan play exactly one instrument, how many students can play exactly twoinstruments?

luanlian · 发表于 2013-11-22 12:33:48

(10+14+11)-20-3*2=9
求证实

yanghaijian · 发表于 2013-11-22 12:48:02

设 students can play exactly twoinstruments为X, 20加3*3*2x等于10加14加11，解出来X等于3

joyxiang007 · 发表于 2013-11-22 13:07:47

luanlian 发表于 2013-11-22 12:33
(10+14+11)-20-3*2=9
求证实

the right answer =3 ;)

joyxiang007 · 发表于 2013-11-22 13:09:43

yanghaijian 发表于 2013-11-22 12:48
设 students can play exactly twoinstruments为X, 20加3*3*2x等于10加14加11，解出来X等于3

thank you so much!!

luanlian · 发表于 2013-11-22 13:40:17

luanlian 发表于 2013-11-22 12:33
(10+14+11)-20-3*2=9
求证实

上面错了;　应该是[(10+14+11)-20-3*3]/2=3　(10+14+11)包含只会一样的即20, 三个同时会三样的，两个仅会两样的。

[原始] How to answer this question in the easiest way.

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