Probability:
In a certain road, 1/3 of the houses have no newspapers delivered. If 1/4 have a national paper delivered and 3/5 have a local paper delivered, what is the probability that a house chosen at random has both?

Assuming that national paper = n, and local = L, I did P(N n L), but the problem is, since this is a mutually exclusive event, won't the P(N n L) = 0?

Question

Probability:
In a certain road, 1/3 of the houses have no newspapers delivered. If 1/4 have a national paper delivered and 3/5 have a local paper delivered, what is the probability that a house chosen at random has both?

Assuming that national paper = n, and local = L, I did P(N n L), but the problem is, since this is a mutually exclusive event, won't the P(N n L) = 0?

anonymous · Answer

I confused whether I should use this formula: P(A u B) = P(A) + P(B) - P(A n B), or this: P(A u B) = P(A) + P(B).

how do I even get P(A n B)???

anonymous · Answer

@tkhunny

tkhunny · Answer

|dw:1407384012079:dw|

tkhunny · Answer

1 - 1/3 = 2/3

2/5 + 1/4 - "The Little Piece" = 2/3

anonymous · Answer

3/5 how 2/5?

anonymous · Answer

@tkhunny

tkhunny · Answer

Show a little fortitude and just fix errors when you encounter them.  I can take it.

3/5 + 1/4 - "The Little Piece" = 2/3

Solve for the little piece.

anonymous · Answer

p(a union b)=2/3

anonymous · Answer

91/60?

tkhunny · Answer

Let's see.  91/60 > 1 -- That doesn't seem right.  Doesn't it have to be less than 1/4?

3/5 + 1/4 - "The Little Piece" = 2/3

12/20 + 5/20 - "The Little Piece" = 2/3

17/20 - "The Little Piece" = 2/3

17/20 - 2/3 = "The Little Piece"

51/20 - 40/3 = "The Little Piece"

Ah!  I see the problem.  Can you fix it?

anonymous · Answer

3/5+1/4+2/3=is it right?

tkhunny · Answer

Did you look at what I showed you?  You have a sign wrong.  The answer must be less than 1/4.  If you get something greater than 1/4, something is very wrong.

anonymous · Answer

11/60

anonymous · Answer

it shows in your equation above 3/5 + 1/4 - "The Little Piece" = 2/3

anonymous · Answer

if 2/3 from right hand side comes lefthand side you will get + sign

anonymous · Answer

51/20 - 40/3 = "The Little Piece"

anonymous · Answer

51-40/60

anonymous · Answer

sorry to budge in, but I keep getting 11/60 for answer?

tkhunny · Answer

Typo Again!

51/60 - 40/60 = "The Little Piece"

Notation is wrong.

51-40/60 = 51 - (40/60) and is NOT what you intend.

Okay, is 11/60 correct?

anonymous · Answer

no. its 11/20 D:

tkhunny · Answer

Let's see:  1/3 + 3/5 + 1/4 - 11/20 = 19/30 Nope.  That is NOT Unity (1)

Let's see:  1/3 + 3/5 + 1/4 - 11/60 = 60/60 = 1  Yup.  That is Unity (1)