If eleven plus two equals one, what does nine plus five equal?

John can eat 27 chocolates in an hour, Jacob can eat 2 chocolates in 10 minutes, and Jolly can eat 7 chocolates in 20 minutes. How long will it take them to share and eat a box of 120 chocolates whilst playing Chess?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

One day, I thought of ways that can be used for creating a palindrome. So I decided that I will turn into a larger number by adding the reversed digits to the original number and keep doing it till I finally obtained a palindrome.

I am not sure if this process will always result in a palindrome eventually but I was able to produce a four-digit palindrome. Can you guess my starting number?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

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?

Why blonde cannot dial 911?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

2 ladies and 2 girls need to cross a river in a boat big enough for 1 LADY or 2 girls. How do they do it?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?