Name a key which is hardest to turn.

Below is the sum of symbols in each row and column in the figure. Analyzing the figure, can you find out the value of the symbols?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

It has horns but can’t beep. It is like to bleat but It is not a sheep. What is it?

100 prisoners are stuck in the prison in solitary cells. The warden of the prison got bored one day and offered them a challenge. He will put one prisoner per day, selected at random (a prisoner can be selected more than once), into a special room with a light bulb and a switch which controls the bulb. No other prisoners can see or control the light bulb. The prisoner in the special room can either turn on the bulb, turn off the bulb or do nothing. On any day, the prisoners can stop this process and say "Every prisoner has been in the special room at least once". If that happens to be true, all the prisoners will be set free. If it is false, then all the prisoners will be executed. The prisoners are given some time to discuss and figure out a solution. How do they ensure they all go free?

I add 5 to 9 and get 2. The answer is correct, so what am I?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Jenifer and Jesica are having a conversation.

Jenifer: I am definitely not over 30.
Jesica: I am 28 and you are surely 5 years older to me at least.
Jenifer: No, you are at least 29.

You are told that both of them are lying throughout in the conversation. Can you find their respective ages?

If two's company, and three's a crowd, then whats four and five ?

Find the missing letter in the last circle logically in the given below picture.