Write the following on standard and expanded form five hundred million eight hundred thirty one thousand nine hundred

Which best explains why this triangle is or is not a right triangle?

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.

When i'm with my factor 5, my prodect is 20 .when i'm with my addend 6' my sum is 10.what number am i