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September 18, 2014

September 18, 2014

Posted by **Kim** on Wednesday, April 7, 2010 at 5:39am.

(a)What is the probability that the student will answer the first six questions correctly and the rest incorrectly?

(b)What is the probability that the student will answer the 1st,2nd,4th,6th,7th,and 10th questions correctly and the rest incorrectly?

(c)How many ways can the student get exactly 6 correct answers?

(d)What is the probability that the student answers exactly 6 questions correctly?

Thank you so much for your help...

- Math -
**Reiny**, Wednesday, April 7, 2010 at 8:11amPrb(right) = 1/3, prb(wrong) = 2/3

a) you want

rrrrrrwwww

prb(rrrrrrwwww) = (1/3)^6(2/3)^4

= 16/59049

b) you want rrwrwrrwwr or the same as above

c) now the order does not matter, you want to choose 6 out of 10 which is

C(10,6) = 10!/(6!4!) = 210

d) prb(6 out of 10) = 210/59049 = 70/19683

- Math -
**Anonymous**, Sunday, April 22, 2012 at 2:19amYou have a 5-question multiple-choice test. Each question has four choices. You don’t know any of the answers. What is the experimental probability that you will guess exactly three out of five questions correctly?

- Math -
**jo**, Tuesday, April 9, 2013 at 11:14amP(3 correct)= (.25)^3 x (.75)^2 combinations; 5C3= 5!/3!2!= 10

answer is 1/64 x 9/16 x 10 = 90/1024

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