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## Comment on

2nd Ball is Yellow## Can we solve this problem

## Sure, give it a try.

Sure, give it a try.

## Hi,

I tried using complement rule, but I got 2/25 instead of 1/25, can you analyze where I went wrong?

P( having second ball yellow)= 1-P( 2nd not being yellow)

= 1-P( 2nd being either red+ 2nd being green)

= 1-(12/25 x 12/24+ 12/25 x 11/24+ 12/25 x 12/24 +12/25 x11/24)

= 1-( 12/25 + 11/25)

= 1-23/25

= 2/25 (what went wrong?)

## It's hard to tell, because

It's hard to tell, because you haven't really explained all of your steps. However, I believe you forgot to include P(1st ball is yellow and 2nd ball is ANY color)

This probability = (1/25)(24/24) = 1/25

I think this is your missing 1/25

## I have a doubt here. The

## In order for the 2nd ball to

In order for the 2nd ball to be yellow, the 1st ball must be NON-YELLOW. So, we have to factor that into our equation.

That is, P(2nd ball yellow) = P(1st ball is not yellow AND 2nd ball is yellow)

We can't just assume that the first ball is not yellow, since there's a 1/25 chance that the first ball is yellow.

Cheers,

Brent

## I don't get it... it says the

SO:

P(any ball AND yellow ball) = 25/25 x 1/24 = 1/24

Why do we have to say that the first ball is NOT yellow...?

WAIT! I think I figured out the answer while typing this... this is true because we have only 1 yellow ball!

TRICKY question! Read the question carefully ya'll.

## Good catch, KB23! :-)

Good catch, KB23! :-)