Puzzles - Number puzzles

Answer

:

13

Explanation

:

As you move from left to right, the sum of the digits in each circle forms a sequence of multiples of 6, from 6 to 30.

Answer

:

6

Explanation

:

Working in rows, the central value equals the difference between the left and right hand values.

Answer

:

18

Explanation

:

Starting on the top left, and moving clockwise around the diagram, add the first two values together to give the next value along. Repeat this sequence.