When we see 2 but call 10?

I am the largest in my family of fifty.
The youngest of our family lives separately from the rest of the family and so do I.
I am regarded as harsh and tough.
I am so large, you cut me in two equal halves,
each half would still be larger than the second largest member of the family.
Who am I?

John is 45 years older than his son Jacob. If you find similarities between their ages, both of their ages contain prime numbers as the digits. Also, John's age is the reverse of Jacob's age.

Can you find their ages?

Your last good ping-pong ball fell into a narrow metal pipe embedded one foot deep in concrete.
How can you get it out undamaged, if all the tools you have are your tennis paddle, shoe laces, and plastic water bottle, which does not fit into the pipe?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

There are five vowels (a, e, i, o, u) in the English language.
Can you tell us a word that contains all these vowels?

There are nine letters in the below-given diagram. You have to form a nine-letter word using these letters.

The more it dries, the wetter it becomes. Can you tell what it is?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

Can you find out the total number of triangles in the given figure?