Can you count the number of triangles in the given figure?

A father's child, a mother's child, yet no one's son.

Who am I?

As you can see that fifteen matches have been used to form an arrangement. What you have to do is remove any six of them to make them ten.

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

On a certain day, John celebrated his birthday. Two days later, his older twin brother Jacob celebrated his birthday.

Is this even possible? How can it be?

Can you find a seven digit number which describes itself. The first digit is the number of zeros in the number. The second digit is the number of ones in the number, etc. For example, in the number 21200, there are 2 zeros, 1 one, 2 twos, 0 threes and 0 fours.

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

An American nightclub called 'The Coconut Grove' had a terrible fire in which over 400 people died. A simple design flaw in the building led to a high death toll. Subsequently, regulations were changed to ensure that all public buildings throughout the country eliminated this one detail, which proved deadly. What was it?