Puzzle | Place numbers 1 to 9 in a Circle such that sum of every triplet in straight line is 15 Improve Improve Like Article Like Save Share Report Place the numbers 1 to 9 in a circle, so that wherever there are three in a straight line they shall add up to 15. SOLUTION: https://media.geeksforgeeks.org/wp-content/uploads/20200710130155/wpv.mp4 The sum of first number and last number is ten ( 1 + 9 = 10 ). Similarly, the sum of second number and second last element is also ten ( 2 + 8 = 10 ) In the same way ( 3 , 7 ) and ( 4 , 6 ) forms two more pairs which add up-to ten. So the four pairs ( 1 , 9 ) , ( 2 , 8 ) , ( 3 , 7 ) , ( 4 , 6 ) occupies the external circles or places. The inner one is occupied by 5. 1 + 9 + 5 =15 2 + 8 + 5 =15 3 + 7 + 5 =15 4 + 6 + 5 =15 The pair elements ( 1 , 9 ) , ( 2 , 8 ) , ( 3 , 7 ) , ( 4 , 6 ) must be placed opposite to each other to attain the required sum. It implies 1 is placed opposite to 9, 2 is placed opposite to 8, 3 is placed opposite to 7 ,4 is placed opposite to 6 and 5 is placed at center. Last Updated : 18 Jan, 2023 Like Article Save Article Previous Puzzle | (Round table coin game) Next Puzzle 21 | (3 Ants and Triangle) Share your thoughts in the comments Add Your Comment Please Login to comment...