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

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

There was a strange boy who was born before his father. How can this be possible?

A professor thinks of two consecutive numbers between 1 and 10.
'A' knows the 1st number and 'B' knows the second number

A: I do not know your number.
B: Nor do I know your number.
A: Now I know.

What are the four solutions for this?

Through your logical capabilities, can you make 7 an even?

John gave half of the apples he had plus one more to Jacob. He gave half of the remaining ones plus one more to James. Now, John was left with just one apple.

Can you find out how many did he have in the beginning?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Nodes are shown below and you need to connect them based on the following rule: Every node can be connected to the number of nodes inside them, i.e. the first node there is a value of 1 which indicates that the first node can connect to exactly one node only.Can you do it?

Can you count the number of triangles in the picture below?

In the city of Brain Teasers, 5% of people do not list their phone numbers. Now if we select random 100 people from the phone directory, then how many people selected will have unlisted phone numbers?