10+10 and 11+11 can give you the same answer.

Explain how?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

There was an aeroplane crash, every single person died, but two people survived. How is this possible?

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

In a boat, the father of a sailor's son is sitting with the son of the sailor. However, the sailor is not present on the boat.

Can this even be possible?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

You measure my life in hours
I serve you by expiring
I vanish faster when I am thin
and slower when I am thick
The wind is my energy
What am I?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

I know a 5-digit number having a property that With a 1 after it, it is three times as large as it would be with a one before it.

Guess the number?

John is the son of Jacob.
So,
Jacob is the_____of John's father?