Number Series Puzzles Questions

5. What numbers should replace the question marks?
  What is the next number?
Answer
Ans = 31 and 4.
12 x 7 = 84; 8 + 12 + 7 + 4 = 31.
6. Which number is the odd one out?
  What is the next number?
Answer
Ans = 6394.
All the others are in pairs where the second and fourth digits change places: 5278/5872, 9416/9614, 7895/7598, 6231/6132.
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