Puzzles - Number puzzles

4.
Answer
:
16
Explanation
:
Starting bottom left and moving clockwise around the triangle, numbers follow the sequence of Square Numbers.

5.
Answer
:
39
Explanation
:
Working from top to bottom, double each number and subtract 1, then 2, then 3 etc.

6.
Answer
:
4
Explanation
:
Working in columns, the sum of the numbers in each column is always 14.