Puzzles - Missing letters puzzles

Exercise : Missing letters puzzles
70.
Answer
:
W
Explanation
:
Starting with the top left outer segment and moving clockwise, letters advance through the alphabet in steps of 4, then 5, 6, 7 etc. The letters in the inner segments follow the same pattern, but move anti-clockwise.

71.
Answer
:
G
Explanation
:
Starting at the top left and working anti-clockwise towards the centre in a spiral, letters advance through the alphabet in steps of 8 at a time.

72.
Answer
:
F
Explanation
:
Taking pairs of letters in adjacent segments, their numerical values always add up to 10.