Solution:

8.

Explanation:
- The Wire of the extension cord-1 is broken.
- The extension cord-6 does not have a wire.
- One of the sockets of cord-2 is broken
- The cord-4 with just one socket is of no use.

Now,
- Cord-1 will connect to the main switch and one of the sockets will connect to Cord-2.
So two sockets can be used from cord-1.

- One of the sockets of cord-2 will connect to the cord-5 and one of them is useless.
So two sockets can be used from cord-2.

- Cord-5 can use all the sockets, i.e. 4

So,
Total In Use = 2 + 2 + 4 = 8.

Please watch the video for a better understanding

Solution:

Tank F.

For an explanation, please visit the video.

Solution:

The Patient will follow the path from room number-13 to room-no.4 as shown in the picture below.

Solution:

Add two squares as shown in the picture below.

Solution:

Image
https://gpuzzles.com/new/img/riddles/Presence-Of-Mind-Picture-Riddle.png
can be changed to
https://gpuzzles.com/new/img/riddles/Presence-Of-Mind-Picture-RiddleAns.png
By adding 3 letters "Ans".

Solution:

U472BMT

Explanation:
The code can be decoded to sound as "U four seven two B M T"
U
four (4)
seven (7)
two (2)
B
M
T

Solution:

Mahrez Pick 4 marbles.

Explanation:
How many marbles Vardy picks, Mahrez needs to make sure that only 1 marble is left after his move, So Vardy needs to pick the last marble.

Example:
If Vardy picks 1, Mahrez picks 5
If Vardy picks 2, Mahrez picks 4
....
...
If Vardy picks 5, Mahrez picks 1

Solution:

31

Explanation:
Ramanujan lighting the candles in binary.
11110 =30
11111 =31

Solution:

3

Explanation:
Digits are represented in binary form where a ball is 1 and a ring is 0.
001 = 1
010 = 2
100 = 4
011 = 3

Solution:

Felix

Explanation:
Iron = Fe (chemical symbol)
59 = LIX (Roman numerals)