A fair five-sided spinner is numbered 1,3,5,7 and 9. Katrina spins it three times. Calculate the probability that the three numbers obtained are the same. Express as a fraction in its lowest terms.

Question

blockcolder · Answer

It's fair, so the probability is (1/5)^3=1/125.

anonymous · Answer

@blockcolder s ryt

parthkohli · Answer

I'm not sure about this but the 5th row of pascal's suggests that it is 1/32 :/

anonymous · Answer

I calculated 1/125 as well. But the marking scheme says it's 1/25. >_<

blockcolder · Answer

Let's do this differently.
There are 5 ways to spin the wheel such that 3 #s are the same.
There are 125 (5^3) possible results on the wheel.
Thus, the probability that 3 #s are the same is 5/125=1/25.
So I was wrong on my first try.

anonymous · Answer

5 ways to spin the wheel? I didn't get that.

anonymous · Answer

it supposed to be an unbiased, i think 1/125 is the corrct answer

blockcolder · Answer

I mean there are 5 possible results wherein the 3 numbers are the same: 111, 333, 555, 777, 999.

anonymous · Answer

OH! Now I get it. Thank you! :D

blockcolder · Answer

No problem. :D

anonymous · Answer

another way to look at this:
makes no difference what the first spin is... so probability = 1
now what is the probability of the second spin matching the first? 1 in 5
and what is the probability of the third one matching them? 1 in 5
so it is 1 (1/5) (1/5) = 1/25