Solution:

The correct choice will be the option 'd'.

In each succeeding row, the previous column is reversed and the lowest digits are omitted.

Solution:

276

Explanation:
6 = 1^1 + 2^1 + 3^1
14 = 1^2 + 2^2 + 3^2
36 = 1^3 + 2^3 + 3^3
98 = 1^4 + 2^4 + 3^4

Thus the next number will be
1^5 + 2^5 + 3^5 = 276

Solution:

The missing number is 11.

Explanation:
The patter here is that the number on the right is half of the product of the other two numbers.

(18*4)/2 = 36
(15*6)/2 = 45

In the same manner,
(8*x)/2 = 44
=> x = 11

Solution:

The missing number is 399.

Explanation:
84 = 4^3 + 3^2 + 4
155 = 5^3 + 5^2 + 5
258 = 6^3 + 6^2 + 6
584 = 8^3 + 8^2 + 8
819 = 9^3 + 9^2 + 9

Thus,
399 = 7^3 + 7^2 + 7

Solution:

23

Explanation:
If you interchange the digits in the squares, you will see that all the resulting numbers are square of some number. Now square root all the thus formed numbers and add them together and you will have the required number in the circle.

In the third figure:
61 = 16 and square root = 4
90 = 09 and square root = 3
18 = 81 and square root = 9
94 = 49 and square root = 7

4 + 3 + 9 + 7 = 23.

Solution:

The missing letter on the first row is H and the missing letter on the third row is L. Beginning from the top right corner, when you begin clockwise, you will have the word Avalanche.

Solution:

The missing letter on left is P and the missing letter on the right is C. The word starts from the missing letter C and forms the word champion.

Solution:

4

Explanation:
5 = Five (four letters) => 4
7 = Seven (five letters) => 5
10 = Ten (three letters) => 3
3 = Three (five letters) => 5

Therefore, 9 = Nine (four letters) => 4.

Therefore the missing number is 4.

Solution:

The number will be 30.

In the first circle
(5 + 4) * 2 = 18

In the third circle
2. (12 + 8) * 3 = 60

In the fourth circle
3. (3 + 9) * 4 = 48

Similarly In the fifth circle
4. (4 + 2) * 5 = 30

Solution:

125

Explanation:
The trick that has been used here is that all the corner digits have been reversed and then added. The sum is than placed in the center.

In the first square:
13 + 32 + 11 + 34 = 90

In the second square:
21 + 19 + 27 + 16 = 83

In the third square:
33 + 33 + 22 + 26 = 125

Thus the missing number is 125