An Unusual Paragraph

This is a most unusual paragraph. How quickly can you find
out what is so unusual about it? It looks so ordinary, you'd
think nothing was wrong with it. Actually, nothing is wrong
with it. But it is not as ordinary as you might think.
If you think about it for a bit, you will find out why it
is truly so unusual. So what is it? What is so unusual about
this paragraph?

Millionaire and Hats

A millionaire bought a job lot of hats 1/4 of which were brown.
He sold 2/3 of the hats including 4/5 of the brown hats.
What fraction of the unsold hats were brown.

Hourglass Puzzle

You have 2 hourglasses, a 7 minute hourglass and an 11 minute
hourglass, what is the quickest way to time the boiling of
an egg for 15 mins?

if a 0.1mm paper is folded 100 times...

if a 0.1mm paper is folded 100 times then what will be the thickness
of it after 100 foldings?

English sentence with all the letters

Would anyone know the shortest sentence in the English language
that has every letter of the alphabet?

Clock Angles

How many times are the hands of a clock at right angle
in a day?

Water jar puzzle

You have three jars that hold max 19, 13 and 7 liters of water
respectively. 13 and 7 litre jars are full of water and 19 litre jar
is empty (so total 20 litres of water).

You can pour water between jars and I want two jars with 10
litres of water (ie 10, 10, 0 from 0, 13, 7)