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

There are two arch enemies Messi and Ronaldo who hate each other to an extreme. One day both were going together and a Jeanie appeared in front of them. Jeanie grants 3 wishes to Ronaldo and one to Messi.

Messi replied smartly 'Give me twice whatever Ronaldo demands'.

Ronaldo asked his 1st wish 'Give me 10000 billion dollars. Soon Messi gets 2000 billion dollars.
Ronaldo asked for his 2nd wish 'Give me one mansion in every country in the world. Soon Messi gets two mansions in every country of the world?

What should be Ronaldo's third wish?

What has many teeth, but cannot bite?

What does man love more than life, and hate more than death or mortal strife; that which satisfied men want; the poor have, and the rich require; the miser spends, the spendthrift saves, and all men carry to their graves?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

If we add four times the age of John four years from now to five times his age five years from now we get ten times his current age.

How old will John be two years from now?

I inserted a coin in a bottle and closed its mouth with the help of a cork. Now, I was able to take the coin out from the bottle without taking out the cork or breaking the bottle. Can you tell me how I did it?

What seven-letter word has hundreds of letters in it?

A rubber ball keeps on bouncing back to 2/3 of the height from which it is dropped. Can you calculate the fraction of its original height that the ball will bounce after it is dropped and it has bounced four times without any hindrance ?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.