what is the solution for this question?

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[Yap Yee Soon]

any different for the highlight sentence?

[Yap Yee Soon]

why nobody answer?

[Cheong Wooi Chun]

please be patient. eventually somebody will answer but it takes time. Many teachers and GCs are busy preparing last minute lesson for students.

[Chong Lee Khim]

Don't be distracted by the highlighted sentence.  Just ignored it and answer as usual.  (use mean = np, P(X=r)= ⁿC_rp^rq^n-r)

[Wong Tok Hua]

Sorry, did not visit engkabang site for quite some time. In my opinion:

a) the mean now shd be 1 + 4(3/4) = 4, since he has solved the puzzle on Monday.

b) the probability that he answers correctly at least 3 days should be the probability that he solves the puzzle correctly for at least 2 days for the remaining 4 days since the outcome for Monday is certain. That means the answer shd be 4C2 (0.75)^2 (0.25)^2 + 4C3 (0.75)^3(0.25)^1 + (0.75)^4

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