Can you circle exactly four of these numbers such that the total is twelve?

1 6 1
6 1 6
1 6 1
6 1 6

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

A time long back, there lived a king who ruled the great kingdom of Trojan House. As a part of the renovation of the kingdom to meet future security needs, he asked his chief architect to lay down a new play in a manner that all of his 10 castles are connected through five straight walls and each wall must connect four castles together. He also asked the architect that at least one of his castles should be protected with walls. The architect could not come up with any solution that served all of King's choices, but he suggested the best plan that you can see in the picture below. Can you find a better solution to serve the king's demand?

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

Steffi's daughter Jazelle needs to be picked up from school every day.
Steffi asks one of her colleagues to pick up Jazelle from the school. Steffi devised a password system to confirm that Jazelle goes with the correct colleague only.

The password on Monday was SJM16.
The password on Wednesday was TAW39.

What will the password be for Friday?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

If there are fifteen crows on a fence and the farmer shoots a third of them, how many crows are left?

Find the next number in the sequence

1, 2, 6, 21, 88, __?

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?