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

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

What has many keys but can’t open a single lock?

What is the below Rebus indicate?

Five lovely ladies(Sophia, Isabella, Madison, Emma and Olivia) planned a picnic.

They each buy one thing each for the picnic.

Sophia, Emma and Olivia got a drink : orange-Juice, apple-juice, and mango-juice.
Olivia got the drink with the same letter as the one in her first name.
Emma loves mango-juice.
The other two bring some food : chocolates and pizza.
Also Madison is allergic to cheese.

So which ladies bought what ?

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

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?

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

Who am I?

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 unordinary about this paragraph?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?