Around the World in Eighty Days: Phileas Fogg started his journey around the world because?

The journey begins because of a bet. Mr. Fogg bets twenty thousand pounds that he can make it around the world in eighty days or less. The club members cannot believe that he would make such a serious bet, but, sure he will fail and they will win twenty thousand pounds, they agree to it, and Mr. Fogg plans to leave that night.