Meet the Billionaires who gave away thier wealth

1. Apple CEO Tim Cook is joining the roster of the very rich who are giving away their wealth. Fortune magazine cited the head of the world's largest technology corporation as saying he planned to donate his estimated $785 million fortune to charity - after paying for his 10-year-old nephew's college education. REUTERS/Robert Galbraith/Files

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Billionaire financier Warren Buffett, Microsoft founder Bill Gates and his wife Melinda Gates are encouraging the very wealthy to give away at least half their worth in their lifetimes through the "Giving Pledge" campaign. REUTERS/Gus Ruelas/Files

Jim Walton and Alice Walton, part of the family that owns Walmart

Sheryl Sandberg, COO of Facebook, and her husband David Goldberg, CEO of SurveyMonkey, are part of The Giving Pledge. 

1.  York City Mayor and founder and CEO of Bloomberg, Michael Bloomberg, is part of The Giving Pledge. REUTERS/Jonathan Ernst/Files

1. NewFormer 

   Former New York City Mayor and founder and CEO of Bloomberg, Michael Bloomberg, is part of The Giving Pledge. REUTERS/Jonathan Ernst/