Answer:
5th graders usually tend to know...
basic multiplication facts usually up to the 12 by 12. (search up "mad minute" to get example of worksheets)
fractions , adding/subtracting fractions, multiplying/dividing fractions, and making fractions have the same denominator
introductions to decimals what are decimals? how to add/subtract decimals
converting decimals to fractions and vice versa (the other way around)
how to divide big numbers! such as using the method of long division
and some 5th graders also tend to learn about mean, mad, mode, outliers, etc.. (things with box plots, histograms, or dot plots.)