The number 40 is decreased to 39. What is the percentage by which the number was decreased, to the nearest tenth of a percent?

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.

If np3 /nc2 = 6, find the value of n

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