Puzzles - Number puzzles

Answer

:

4

Explanation

:

The average of the numbers in each column is always 4.

Answer

:

9

Explanation

:

Using the top two grids as a source, numbers in the lower left grid equal the sums of numbers in corresponding positions of the top two grids, subtracting 1 each time, and numbers in the lower right grid equal the differences between numbers in corresponding positions of the top two grids, adding 1 each time.

Answer

:

19

Explanation

:

Divide the diagram in half, horizontally and vertically, to give 4 squares, each 3x3. In each square, add up the 4 outer numbers, and put the result in the space in the centre.