Final answer:
The probability that a couple with at least one girl has two girls is 0.5 or 50%.
Step-by-step explanation:
The question asks for the probability of a certain couple having two girls given that they have at least one girl. To solve this, we need to consider the sample space of all possible outcomes and the favorable outcomes. Let's assume the genders of the couple's children can be either male (M) or female (F).
The sample space includes the following outcomes: MM, MF, FM, and FF. Out of these, the favorable outcomes are FM and FF (as at least one of the children is a girl). Therefore, there are two favorable outcomes out of four possible outcomes.
The probability of the couple having two girls, given that they have at least one girl, is 2/4 or 1/2, which can be simplified to 0.5 or 50%.