Round 827.3 to 3 significant figures

To round to three significant figures, look at the fourth significant figure. It's a 5 , so round up.

To round to four significant figures, look at the fifth significant figure. It's a 1 , so round down.

To round to two significant figures, look at the third significant figure. It's an 8 , so round up.

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this