CAT 2017 [slot 2] Question with solution 01

Answer: 3
Explanation:
The square grid is filled by 9 numbers from 1 to 9. Their sum (1 + 2 + 3 +... 9) equals 45. Since the sum of numbers in each row and each column and each diagonal must be equal, the sum of terms in each row and in each column and in each diagonal, must be 15. For this to happen, the middle element in the 2nd row and the 2nd column must be the middle-most term of the 9 terms, i.e. 5.
The corner elements in the first row are 6 and 2 (given), so the middle element in the first row must be 7. In the 2nd column, the top most element is 7 and the middle element is 5, so the bottom row middle element must be 3.