Puzzle 1: Which number replaces the question mark?
Answer: 45
Consider diagonally
15 + 15 = 30 35 + 5 = 40
30 + 15 = 45 40 + 5 = 45
60 + 15 = 75 50 + 5 = 55
Puzzle 2: Which number replaces the question mark?
3, 5, 13, 43, 177, ?, 5353
Answer: 891
3 x 1+ 2 = 5
5 x 2 + 3 = 13
13 x 3 + 4 = 43
43 x 4 + 5 = 177
177 x 5 + 6 = 891
891 x 6 + 7 = 5353
Puzzle 3: Which number replaces the question mark?
Answer: 7
Sum of the numbers in each part is 25.
8 + 5 + 5 + ? = 25
? = 25 – 18
? = 7
Puzzle 4: Which number replaces the question mark?
If 2 + 3 = 8
3 + 7 = 27
4 + 5 = 32
5 + 8 = 60
6 + 7 = 72
Then 7 + 8 =?
Answer: 98
This equations follow the following logic;
2 + 3 = (2 x 3) + (2 x 1) = 6 + 2 = 8;
3 + 7 = (3 x 7) + (3 x 2) = 21 + 6 = 27;
4 + 5 = (4 x 5) + (4 x 3) = 20 + 12 = 32;
5 + 8 = (5 x 8) + (5 x 4) = 40 + 20 = 60;
6 + 7 = (6 x 7) + (6 x 5) = 42 + 30 = 72;
So to find the missing number;
7 + 8 = (7 x 8) + (7 x 6) = 56 + 42 = 98.