Brain teaser for the week 20200926 每周烧次脑
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Difficulty level: ✮ ✮
How many different committees can be formed from a pool of three people, where a committee can consist of one to three people?
假如从一个3人群中成立一个委员会，成员数可以从1至3人均可，那么一共有多少种组合？
(a) 3
(b) 4
(c) 5
(d) 6
(e) 7
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Answer to be disclosed at our
next episode of brain teaser
答案下期公布
By the New Year's Day, top 3 players
will get a gift from us!
元旦前，年度前三高手将获得神秘礼物！
Answer to the last week 上期答案 Brain teaser for the week 20200919 每周烧次脑
(C) There is the same amount of water in the alcoholas alcohol in the water.
Let’s say the cup of alcohol you pour in the water contains c gallons (c could be1/10, for example). Now the water bucket has a mixture of alcohol and water. Now you pour one cup (again, c gallons) of that mixture back into the alcohol bucket. Let’s say there are a gallons of alcohol and w gallons of water in that cup. So (1) a + w = c.
Now the amount of water poured into the alcohol is w. The amount of alcohol in the water bucket is c – a, since we poured a gallons of alcohol into the alcohol bucket from the water bucket. From (1) we get c – a = w, so (c) is true.
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