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:

100

Series of number that do not contain albhabet 'T'

Solution:

The number 20 fits in place of question mark.

This is because (number in first column) / (number in second column) * 8 = number in third column.

Here (left number / middle number) * 8 = right number
E.g. (35 / 20) * 8 = (7/4) * 8 = 7 x 2 = 14
The same process can be used to find out the missing digit.

Solution:

Q

Explanation:
First Square:
6 + 4 + 4 = 14
N is the 14th letter.

Second Square:
4 + 1 + 7 = 12
L is the 12th letter.

Third Square:
5 + 6 + 10 = 21
U is the 21st letter.

Fourth Square:
14 + 2 + 1 = 17
Q is the 17th letter.

Solution:

13 8

prime number and then number of letter in prime number

examples
2 (two - 3 letters) => 2,3
3 (three - 5 letters) =>3,5

Solution:

97

Explanation:

Difference between number sequence is below:
9,14,19,24,29

Now the difference between above sequence is 5.

So next number is 68 + 29 =>97

Solution:

54325

Explanation:

Consider 1 = 5
2 = 25
3 = 325
4 = 4325
Then 5 = 54325

See the pattern. With every digit, the previous numbers are added after that digit

So the next number in the series is 54325

Solution:

3 1 2 2 1 1
1 3 1 1 2 2 2 1

Read Line as one 1 => 1
Read Line 2 as two one => 2 1
Read Line 3 as one two and one one => 1 2 1 1
and so on.

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:

143547

Solution:

0

Explanation:
1 * 1 * 1 = One
2 * 2 * 2 = Eight
3 * 3 * 3 = Twenty seven
4 * 4 * 4 = Sixty Four
For all the above, you can see that the first letter of the sum is the code.
Thus 5 * 5 * 5 = One twenty five

Thus 555 = O.