Each of the integers from 1 to 12 is to be placed in one of the circles in the figure so that the sum of the integers along each side of the figure is 25. Determine the sum of the four integers placed in the corners.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Same as my way to solve it
Great solution @Kay Xspre
Nice solution. But is such an arrangement possible?
Log in to reply
Example
An example is provided one here. There may be other possible arrangement as well.
Log in to reply
I wrote a program to find all of the solutions. There are 656 real solutions (once duplicates are accounted for). Only 41 answers exist if you only count unique corners as a solution.
1 + 2 + 3 . . . + 1 2 = 2 1 2 × 1 3 = 7 8 , where, each number counted once. If we add the numbers along sides, e.g. consider this square as ABCD, now if we add the numbers along side AB and side DA, then the number on corner A is counted twice. Similarly if we add up the numbers along 4 sides it will include the 4 corner numbers twice and the sum becomes as 2 5 × 4 = 1 0 0 . Hence the sum of numbers in 4 corners = 1 0 0 − 7 8 = 2 2 .
I brute-forced it with:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 |
|
easy. 1+4+7+10=22. hahaha
I came up with arrangement 12 8 4 1 on top, 12 2 5 6 going down left side, 1 10 11 3 going down right side and 6 9 7 3 on bottom.
Problem Loading...
Note Loading...
Set Loading...
The sum of all numbers from 1 to 12 is 2 1 2 × 1 3 = 7 8 , however, this does not take account that the corners were count twice in summing the sum of each side. Given the sum for all sides (when the corner was counted twice) is 2 5 × 4 = 1 0 0 , the corner shall have the sum of 1 0 0 − 7 8 = 2 2