Solution:

Let's say the Mice are X and Y and Bottle are B1, B2....B9

Step1:
X drinks B1 B2 & B3
Y drinks B1 B4 & B5

Possible Outcomes
If both mice die, B1 is the poison bottle.
If only mice X dies, Either B2 or B3 is the poison bottle.
If only mice Y dies, Either B4 or B5 is the poison bottle.
If nobody dies, Poison is in B6 B7 B8 or B9


Step2: (If nobody dies)
X drinks B6 B7
Y drinks B6 B8

Possible Outcomes
If both mice die, B6 is the poison bottle.
If only mice X dies, B7 is the poison bottle.
If only mice Y dies, B8 is the poison bottle.
If nobody dies, B9 is the poison bottle.

Step2: (Only X dies - Either B2 or B3 is the poison bottle)
Y drinks B2, if Y dies B2 is the poison bottle else B3

Step2: (Only Y dies - Either B4 or B5 is the poison bottle)
X drinks B4, if X dies B4 is the poison bottle else B5

Solution:

Playing chess

Game needs two players so Brother-8 is playing chess with Brother-2

Solution:

If we have to measure precisely, it is impossible. Because we are asked to measure odd number of liters whereas all the jars we have can contain only even liters of water.

* Tricky question asked in ias/infosys/infoedge/ibibo interview

Solution:

45 minutes

Explanation :
All you have to do is burn the first rope from both the ends and the second rope from one end only simultaneously. The first rope will burn in 30 minutes (half of an hour since we burned from both sides) while the other rope would have burnt half. At this moment, light the second rope from the other end as well. Where, the second rope would have taken half an hour more to burn completely, it will take just 15 minutes as we have lit it from the other end too.

Thus you have successfully calculated 30+15 = 45 minutes with the help of the two given ropes.

Solution:

12 steps:

Steps 11 Liter jug 6 Liter Jug
1. 11 -
2. 5 6
3. 5 0
4. 0 5
5. 11 5
6. 10 6
7. 10 0
8. 4 6
9. 4 0
10. 0 4
11. 11 4
12. 9 6 ==> i found 9 liter in 11liter jug(as required)

Solution:

Step 5 is invalid, because we are dividing by (x-y), and since x=y, we are thus dividing by 0. This is an invalid mathematical operation (division by 0), and so by not following basic mathematical rules

Solution:

Just One!

example
If u get Blue rock with label as "blue+red" => this is red as all labels are wrong.
In this way u can logically solve this puzzle.

Solution:

Wristwatches

Most of us must have assumed the answer to be a ring in the wrong finger but that's not the case as it's a normal ring. The error is in the watch. Wristwatches are manufactured with the adjustment pin always on the right side.

Solution:

7

Explanation:
Put batteries into 3 groups: two groups of 3 and one group of 2.
It guarantees at least one of the group has got two working battery
Group of 3 requires 3 attempts to verify if 2 batteries of the group are working (B1+B2, B2+B3, and B1+B3) while the group of 2 requires one attempt (B1+B2)
Total attempts = 3 + 3 + 1 = 7

Solution:

8 Steps

Explanation:
Steps------2L Gallon-------5L Gallon
A-------------12-------------0
B-------------07-------------5
C-------------07-------------0
D-------------02-------------5
E-------------02-------------0
F-------------00-------------2
G-------------12-------------2
H-------------09-------------5