1/3 of a class are girls.
a) What is the ratio girls to boys in the class?
b) What is the ratio boys to girls in the class?

Ratio of girls to boys is (1/3*X) / (2/3*X).

That is, 1:2

Similarly, ratio of boys to girls is (2/3*X) / (1/3*X).

That is, 2:1

Step-by-step explanation:

Assume, total Number of students in the class is X.  Since, 1/3 part of the class is girls, this makes 2/3 part of the class boys. Total number of girls will be equal to 1/3 *X. Total number of boys is equal to 2/3*X. So, ratio of girls to boys is (1/3*X) / (2/3*X). That is, 1:2. Similarly, ratio of boys to girls is (2/3*X) / (1/3*X). That is, 2:1

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