Posted by **poe** on Thursday, June 17, 2010 at 6:25pm.

A test is composed of six multiple choice questions where each question has 4 choices. If the answer choices for each question are equally likely, find the probability of answering 3 OR 4 questions correctly.

- Math - probability -
**Writeacher**, Thursday, June 17, 2010 at 7:08pm
Please type your __subject__ in the **School Subject** box. Any other words, including obscure abbreviations, are likely to delay responses from a teacher who knows that subject well.

- college -
**Reiny**, Thursday, June 17, 2010 at 8:28pm
R --- right

W --- wrong

so we want the case of

RRRWWW or RRRRWW and its possible arrangements

P(3 R) = C(6,3)(1/4^3(3/4)^3 = .131836

P(4 R) = C(6,4)(1/4)^4(3/4)^2 = .032959

P(3R or 4R) = the sum of those two

= .1648

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