Why do we preferably have round manhole covers and not square ones?

Can you find the odd number in the following?

2716, 4135, 5321 and 7145

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

Can you tell a 3D object that has just two surfaces?

What is the difference between a jeweller and a jailer?

What word begins and ends with an E, but has only one letter?

There are hundred red gems and hundred blue gems. The blue gems are priceless while the red gems equal wastage. You have two sacks one labeled Heads and the other Tails. You have to distribute the gems as you want in the two sacks. Then a coin will be flipped and you will be asked to pick up a gem randomly from the corresponding sacks.

How will you distribute the gems between the sacks so that the odds of picking a Blue gem are maximum?

I am a word that begins with the letter “i.” If you add the letter “a” to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?

A man is walking down a road with a basket of eggs. As he
is walking he meets someone who buys one-half of his eggs
plus one-half of an egg.
He walks a little further and meets another person who buys
one-half of his eggs plus one-half of an egg.
After proceeding further he meets another person who buys
one-half of his eggs plus one half an egg. At this point, he
has sold all of his eggs, and he never broke an egg.
How many eggs did the man have to start with?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?