What number should come in place of question mark?
23
Interchange the digits in the square. You will find that all these number are squares of some or other number. Now, the number inside the circle is the sum of square roots of the numbers in squares.
In the 3rd diagram, 61 = 16 and square root = 4
90 = 09 and square root = 3
18 = 81 and square root = 9
94 = 49 and square root = 7
4 + 3 + 9 + 7 = 23.
