4 freshman boys, 6 freshman girls, and 6 sophomore boys go on a trip. How many sophomore girls must join them if a student's gender and class are to be independent when a student is selected at random?

4 sophomore girls .

Step-by-step explanation:

If a student's gender and class are to be independent when a student is selected at random, two conditions must be met:

n° boys = n° girls

n° freshmen = n° sophomore

Currently, there are 10 boys and 6 girls, thus 4 girls must join.

Currently, there are 10 freshmen and 6 sophomores, thus 4 sophomores must join.

Therefore, 4 sophomore girls must join.

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Step-by-step explanation: