What number should be removed from the list {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13} so that the mean of the remaining numbers is 7.25?

4 should be removed

Step-by-step explanation:

Just do a process of elimination and work through the numbers.

18

step-by-step explanation:

draw the shape and you will see that f and k are actually at adjacent vertices (points of the hexagon that are neighboring).   so find the distance between (1,2) and (4,2).   that is easy since (1,2) and (4,2) is just a vertical distance to count, which is 3.   it is a regular polygon which means all sides are congruent.   you have 6 sides (hexa) so multiply 6 by 3 to receive 18.