# Sign on the pumps at a gas station encourages customers to have their oil checked, and claims that one out of 6 cars needs to have oil added?

A. One out of the next four cars needs oil.

Probability =

B. Two out of the next eight cars needs oil.

Probability =

C. 10 out of the next 40 cars needs oil.

Probability =

### 1 Answer

Relevance

- PuzzlingLv 74 weeks ago
Use the binomial probability formula.

P(X = k) = C(n,k) * p^k * q^(n-k)

n : number of trials (4)

k : number of successes (1)

p : probability of success (1/6)

q : probability of failure (1 - p = 5/6)

P(X = 1) = C(4,1) * (1/6)^1 * (5/6)^3

= 4 * 125/1296

= 500/1296

= 125/324 (or ~38.6%)

P.S. C(n,k) is the "n choose k" formula

C(n,k) = n! / (k! (n-k)!)

Now you should have all the information needed to solve B and C.

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I think you mean 125/324.