Puzzles - Missing letters puzzles

Exercise : Missing letters puzzles
49.
Answer
:
S
Explanation
:
Taking pairs of letters in the inner and outer segments of each eighth of the diagram, the numerical values always add up to 20.

50.
Answer
:
K
Explanation
:
Working in columns, add together the numerical values of the first and second letters, and put the letter with the reverse alphabetical value of this sum in the bottom space.

51.
Answer
:
S
Explanation
:
Starting with the G, move clockwise around the circle, in steps of 3 letters, then 4, 5, 6 and 7.