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.
- 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.
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
- Equation of straight line passing through a given point which bisects it into two equal line segments
- Puzzle | Maximum pieces that can be cut from a Circle using 6 straight lines
- Puzzle | Draw 4 straight line in 3*3 matrix (9 dots)
- Represent a given set of points by the best possible straight line
- Length of the normal from origin on a straight line whose intercepts are given
- Area of triangle formed by the axes of co-ordinates and a given straight line
- Straight-line Number
- Check whether a straight line can be formed using N co-ordinate points
- Puzzle 81 | 100 people in a circle with gun puzzle
- Puzzle | Divide crescent moon into 6 parts in just two straight lines
- Puzzle | Connect 9 circles each arranged at center of a Matrix using 3 straight lines
- Print numbers such that no two consecutive numbers are co-prime and every three consecutive numbers are co-prime
- Check if every vertex triplet in graph contains two vertices connected to third vertex
- Color all boxes in line such that every M consecutive boxes are unique
- Equation of circle when three points on the circle are given
- Check if a circle lies inside another circle or not
- Angle subtended by the chord to center of the circle when the angle subtended by the another equal chord of a congruent circle is given
- Area of the circle that has a square and a circle inscribed in it
- Check if it is possible to create a matrix such that every row has A 1s and every column has B 1s
- Total number of ways to place X and Y at n places such that no two X are together
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.