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Xavier, Yvonne, and Zelda each try independently to solve a [#permalink]
19 Jun 2008, 23:58

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Difficulty:

15% (low)

Question Stats:

85% (01:36) correct
14% (01:04) wrong based on 162 sessions

Xavier, Yvonne, and Zelda each try independently to solve a problem. If their individual probabilities for success are 1/4, 1/2 and 5/8, respectively, what is the probability that Xavier and Yvonne, but not Zelda, will solve the problem?

OG C# 231 Xavier, Yvonne, Zelda each try independently to solve a problem. If their individual probabilities for success are 1/4, 1/2, and 5/8, repectively, what is the probability that xavier and yvonne, but not zelda, will solve the problem? Please provide solution with explanation. THanks a. 11/8 b. 7/8 c. 9/64 d. 5/64 e. 3/64

P(Xavier will solve)=1/4 P(Yvonne will solve)=1/2 P(Zelda will NOT solve) = 1- 5/8 = 3/8.

Now, we need to multiply all this Ps to find an answer: p= (1/4)*(1/2)*(3/8) = 3/64.

Now, we need to multiply all this Ps to find an answer: p= (1/4)*(1/2)*(3/8) = 3/64.

I always get confused, Why don't we multiply it by 3? because these independent event can occur is any order. that means it can also be (3/8)*(1/4)*(1/2) ?
_________________

Life is very similar to a boxing ring. Defeat is not final when you fall down… It is final when you refuse to get up and fight back!

I'm not great with probability so double check whatever I say, but we're not looking for the order in which X and Y get it right and Z get's it wrong. We're just looking for the probability of X and Y getting it right while Z get's it wrong. It doesn't matter in what order they get it right or wrong, all that matters is how they perform. Think of it like flipping a coin a few times and recording the probability of getting heads. It doesn't matter if you get two heads in a row then one tails, or one tails then two heads in a row. The probability is the same either way. This is in contrast to say, the chances of gettign a certain color gum ball in a certain order.

Hope that helps!

nikhil007 wrote:

greenoak wrote:

Quote:

OG C# 231

Now, we need to multiply all this Ps to find an answer: p= (1/4)*(1/2)*(3/8) = 3/64.

I always get confused, Why don't we multiply it by 3? because these independent event can occur is any order. that means it can also be (3/8)*(1/4)*(1/2) ?