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At a gas station, 50% of the customers use regular gas, 30% use mid-grade gas and 20% use premium gas. Of those customers using regular gas, only 30% fill their tanks. Of those customers using mid-grade gas, 60% fill their tanks, whereas of those using premium, 50% fill their tanks. If the next customer fills the tank, what is the probability that he uses premium gas

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pedrocarratore

Answer:

The probability is 0.2326 or 23.26%.

Step-by-step explanation:

The probability that a random customer fills their tank with premium gas is:

[tex]P( prem\ \&\ fill) = 0.2*0.5=0.10[/tex]

The probability that a random customer fills their tank is given by:

[tex]P(fill)=P( reg\ \&\ fill)+P( mid\ \&\ fill)+P( prem\ \&\ fill)\\P(fill) = 0.5*0.3+0.3*0.6+0.2*0.5\\P(fill) = 0.43[/tex]

Therefore, the probability that a customer used premium gas given that hey have filled their tank is:

[tex]P(prem| fill) = \frac{P( prem\ \&\ fill) }{P(fill)} \\P(prem| fill) =\frac{0.10}{0.43}=0.2326[/tex]

The probability is 0.2326 or 23.26%.

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