Numbers in a Plus
Consider a normal five unit plus(+) shaped grid. What is the distinct number of ways to place without repetition in each of the squares of this grid?
Details and assumptions -
Rotations are not considered to be distinct.
The answer is 30.
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1 solution
Note that for every choice of a number in the central square, there are ( 4 − 1 ) ! choices for the other places to be filled (by using the formula for circular permutations.). And the central square can be filled in 5 ways. Thus total number of ways= 5 ∗ 3 ! = 3 0 .