Slightly outnumbered

If this class contains between $45$% and $50$% girls, what is the smallest possible number of girls in the class?
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Problem

 

In Miss Quaffley's class, the girls make up more than $45$% of the pupils, but less than $50$%.

What is the smallest possible number of girls in her class?

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.