How rich are the world’s richest people? According to Forbes’ 2015 Billionaires list, the 500 people with the most money collectively have a whopping $4.7 trillion to their names. The top 20 together are worth nearly $900 billion, and their wealth comes from sources as diverse as beauty products and the internet.

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20. Sergey Brin
Worth $29.2 billion, Brin co-founded Google with Larry Page when both were still students at Stanford. He's director of special projects at Google. Brin was born in the former Soviet Union and was six when his family moved to the US.

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19. Larry Page
The Google co-founder and CEO is worth $29.7 billion. He is generous to charities and passionate about clean energy, which helps explain why he's also invested in Tesla Motors, the electric-car company.

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18. Sheldon Adelson
At 81, Adelson has been in business for nearly seven decades, having started his first venture, selling newspapers, when he was 12. His $31.4 billion comes mainly from casinos and he's chairman and CEO of the world's largest gaming company, Las Vegas Sands.

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17. Sir Li Ka-shing
The 87-year-old Hong Kong businessman, who never finished high school, is the richest person in Asia, with a fortune of $33.3 billion. He is chairman of the boards of Hutchison Whampoa Limited and Cheung Kong Holdings and the sources of his wealth range from container ports to retail.

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16. Mark Zuckerberg
Only 31, the Facebook chairman, CEO and co-founder is worth $33.4 billion and the youngest billionaire in the top 20. The Harvard dropout is a noted philanthropist who in 2013 topped the Chronicle of Philanthropy's list of most generous Americans.

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15. Jeff Bezos
The Amazon.com founder and CEO had $34.8 billion to his name according to Forbes' 2015 Billionaires ranking. However, in July this year he actually shot up to fifth place when a surge in Amazon stock earned him a cool $7 billion in less than an hour.

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14. Michael Bloomberg
The former New York City mayor is once again CEO of Bloomberg LP, the news and information company he founded in the early 1980s with the $10 million severance package he got after being laid off from an investment bank. He's now worth $35.5 billion.

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13. Bernard Arnault and Family
Worth $37.2 billion, Bernard Arnault is chairman and CEO of luxury-goods company LVMH. He started out in his father's construction business but steered that company towards luxury goods in the 1980s, buying the company that owned Christian Dior at the time.

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12. S. Robson Walton
Wal-Mart founder Sam Walton's eldest child is chairman of the board at the world's largest retailer. Most of this lawyer's $39.1 billion comes from his Wal-Mart inheritance, but he also has a valuable stake in Hyatt Hotels.

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11. Alice Walton
The youngest of Wal-Mart founder Sam Walton's children, Alice Walton inherited her $39.4 billion fortune. She used to be involved in the family's bank Arvest but is now known especially for curating art, being the founder of the Crystal Bridges Museum of American Art.

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10. Liliane Bettencourt and Family
Not only the richest person in France but also Europe's richest woman, Bettencourt inherited cosmetics giant L'Oreal, which her father had started, in 1957 and is worth $40.1 billion. The 92-year-old was involved in running the company until 2012, when she was replaced by her grandson after a legal battle.

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9. Jim Walton
The third of Wal-Mart founder Sam Walton's four children, Jim Walton is chairman and CEO of Arvest Bank, which was founded by his family. However, most of his $40.6 billion comes from his Wal-Mart inheritance.

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8. Christy Walton and Family
For five of the past six years, Christy Walton has been the world's richest woman. Known for her philanthropy, she inherited her $41.7 billion fortune upon the death of her husband John, a Wal-Mart heir who had also made a smart investment in solar panels.

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7. Charles Koch
The elder one of the Koch brothers is the chairman and CEO of Koch Industries, which has stakes in everything from oil pipelines to paper towels. The brothers inherited the business from their father and expanded it so that they each is now worth $42.9 billion.

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6. David Koch
At 75, David is four years younger than his brother Charles. David serves as executive vice president of Koch Industries and, like his brother, is worth $42.9 billion.

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5. Larry Ellison
The founder of Oracle is worth $54.3 billion and a pioneer among tech entrepreneurs. He loves the good life, is fanatic about yachting and is a licenced pilot.

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4. Amancio Ortega
Spain's richest man made his money through clothing chain Zara, which has also made him the richest retailer in the world. Ortega is worth $64.5 billion.

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3. Warren Buffet
At 84, Buffett famously still lives in the same house that he bought in 1958 and has pledged to give away 99% of his money to charitable causes. His fortune, worth $72.7 billion, comes from his company Berkshire Hathaway, which has stakes in insurance, energy and railroads.

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2. Carlos Slim Helu and Family
Carlos Slim Helu made his $77.1 billion fortune through telecom in Latin America, making him and his children the richest people in Mexico. The 75-year-old has now diversified and owns the majority stake in the New York Times.

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1. Bill Gates
With $79.2 billion to his name, the Microsoft founder has been the world's richest person for 16 years out of the last 21. He's not keeping everything to himself, though: He has already given away nearly $30 billion to good causes, among them the Bill & Melinda Gates Foundation.
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