Math Is Fun Forum

NESIC

Member

Registered: 2010-09-25

Posts: 16

Dear All help me to resolve problem

A paint store chain provides and sells latex and semigloss paint. Based on long range sales, the probability that a customer will purchase latex is .75. Of those that purchase latex paint, 60% also purchase rollers but 30% of semigloss buyers purchase rollers. A randomly selected buyer purchases a roller and a can of paint. What is the probability that the paint is latex.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Dear All help me to resolve problem

Hi NESIC;

This is an exam question. Please show me what work you have done on it.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Candide

Member

Registered: 2010-09-30

Posts: 3

Re: Dear All help me to resolve problem

This question is about conditional probabilities.

First step is to see what you have:

P(latex)=0.75

P(rollers | latex)=0.6

P(rollers | semigloss)=0.3

2nd step is too determine what is asked for:

P( latex | roller) = ?

According to Bayes theorem:

Since the value of P(S) is not given, we have to make an assumption: Every customer buys either latex or semigloss plaint. Therefore P(semigloss)=P(S)=1-P(L)=0.25.

The probability that the paint in latex is then 85.7%.

Hope this is correct.

Last edited by Candide (2010-09-30 09:44:24)

NESIC

Member

Registered: 2010-09-25

Posts: 16

Re: Dear All help me to resolve problem

Hi Candide;

thanks for your help