[عاشقة المساء]

a) In a 10- question examination, each question is worth 10 points and it is graded right or wrong, considering the individual questions, in how many ways can a student score 80 or better?


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b)The director of research and development for a company has nine scientists who are equally qualified to work on projects A, B and C. In how many ways can the director assign three scientists to each project ?


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c)In how many ways can seven of ten books be arranged on a bookshelf? In how many ways can all ten books be arranged on the shelf?