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**1. The problem statement, all variables and given/known data**

In a neighbourhood, 75% of households speak only English at home, and 5% speak only Spanish at home.

Four households are randomly chosen. Given that at least one of the four households speaks only Spanish at home, what is the probability that only one speaks Spanish at home?

**2. Relevant equations**

P(B|A) = P(B&A)/P(A)

A = event that at least one of the four households speak only Spanish

B = event that exactly one speaks only Spanish

**3. The attempt at a solution**

P(A) = 1 - (75/100)(74/99)(73/98)(72/97)

*(1 - prob. that none speak Spanish)*

**P(B&A) = ?**

Does P(B&A) = P(B)? Which would mean P(B) = 4(75/100)(74/99)(73/98)(5/97)

**Attempted solution: P(B|A) = 0.125**

Thanks in advance! :)