A student attempts 3 multiple choice questions each has 6 answ. By guessing randomly what is the probability he gets at least 1 asw correct? (hint use tree diagram)

Question

anonymous · Answer

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anonymous · Answer

a) 75/216
b) 3/4
c) 16/216
d) 25/216
d) 91/216

anonymous · Answer

i am gettin 86/216 which isn't correct

anonymous · Answer

can u show ur work?

anonymous · Answer

yep, juss downloading

kropot72 · Answer

The probability of getting zero answers correct is
$$(1-\frac{1}{6})^{3}=(\frac{5}{6})^{3}$$
The probability of getting 1 or more answers correct is given by
$$P(1\ or\ more\ answers\ correct)=1-(\frac{5}{6})^{3}=\frac{91}{216}$$

anonymous · Answer

attachment

anonymous · Answer

@kropot72 what theorem r u usin?

anonymous · Answer

@kropot72 's answer is right.

kropot72 · Answer

I just used number theory. The probability of getting one question wrong is 5/6. The probability of getting all three questions wrong is
$$\frac{5}{6}\times\frac{5}{6}\times\frac{5}{6}=(\frac{5}{6})^{3}$$
The sum of the probabilities of all the outcomes must equal 1.Therefore the probability of getting one or more answers correct is
$$1-(\frac{5}{6})^{3}$$

anonymous · Answer

kropot is genius

kropot72 · Answer

No way.

anonymous · Answer

i had missed out one branch i got 91/216 but i'm interested in what formular or theory u r using

anonymous · Answer

so...

anonymous · Answer

if you just use common sense and think about this

anonymous · Answer

the chance of having all the possible outcome is 100% right?

anonymous · Answer

kropot just figured out the chance of it not happening, then subtract it from all the possible outcome. That's why it's 1-(5/6)^3

anonymous · Answer

ok, thx