Find the probability that when a couple has three children, at least one of them is a girl. (Assume that boys and girls are equally likely.)

Step 1 ：Given that the probability of having a boy or a girl is \(\frac{1}{2}\).

Step 2 ：The only way to not have at least one girl is if all three children are boys.

Step 3 ：The probability of having three boys is \(\left(\frac{1}{2}\right) * \left(\frac{1}{2}\right) * \left(\frac{1}{2}\right) = \frac{1}{8}\).

Step 4 ：Therefore, the probability of having at least one girl is 1 - the probability of having all boys.

Step 5 ：Substituting the values, we get \(1 - \frac{1}{8} = \frac{7}{8}\) or 0.875.

Step 6 ：Final Answer: The probability that when a couple has three children, at least one of them is a girl is \(\boxed{0.875}\).