The probability of sunshine on any given day in July for a town is 75%. The probability of rain is 25%.

What is the probability of sunshine 3 days in a row?

What is the probability of rain at least once during a week?

P(sunshine 3 days in a row) = (.75)^3 ≈ 0.42 ≈ 42%

P (rain at least once during the week) =

1 - P( of no rain during the week ) =

1 - (.75)^ 7 ≈ .87 ≈ 87%