问题 填空题

现有7件互不相同的产品,其中有4件次品,3件正品,每次从中任取一件测试,直到4件次品全被测出为止,则第三件次品恰好在第4次被测出的所有检测方法有______种.

答案

第三件次品恰好在第4次被测出,说明第四次测出的是次品,而前三次有一次没有测出次品,最后一件次品可能在第五次被测出,第六次,或者第七次被测出,由此知最后一件次品被检测出可以分为三类,故所有的检测方法有 C31×C31×C41×C31×C21×(1+2×1+2×1×1)=1080

故答案为:1080.

完形填空

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

If you are hungry, what do you do? Have your favorite meal and stay quiet after that?  71  But it never lets you know, because you keep it busy thinking about your friends or favorite stars.So it silently serves your needs and never lets itself grow.When mind loses its freedom to grow, creativity gets a full stop.This might be the reason why we all sometimes think "What happens next?", "Why can't I think?"

  72  Why reading but not watching TV? It is because reading has been the most educative tool used by us right from childhood.Since it develops other aspects of our life, we have to get help from reading.

Once you read a book, you run your eyes through the lines and your mind tries to explain something to you.  73 Now this seed is unknowingly used by you to develop new ideas.If it is used many times, the same seed can give you great help to relate a lot of things which you would have never thought of in your wildest dreams!

This is nothing but creativity.  74  Within no time you can start talking with your friends in English or any other language and never run out of the right words.

So guys, do give food for your thoughts by reading, reading and more reading.  75 Go and get a book!

A.The interesting part of the book is stored in your mind as a seed.

B.Why not do some reading while you are hungry?

C.Just like your stomach, your mind is also hungry.

D.Now what are you waiting for? E.Hunger of the mind can be actually solved through wide reading.

F.Reading can help you make more friends, too.

G.Also this makes a significant contribution to your vocabulary.

单项选择题