But the pair almost didn't meet.
On July 5, 1991, Buffett was visiting Washington state when he was invited to dinner with Gates' parents via a mutual friend. The friend teased the possibility that Gates himself might show up, according to Buffett, who told students the story during an event with Gates at the University of Nebraska at Lincoln's College of Business Administration in 2005.
Meanwhile, Gates protested his invitation.
"It was a funny event because my mom's very sociable, always getting people together," Gates tells the students. "I at this time didn't believe in vacations, was totally focused on my job. So when she said to me, 'You've got to come out and meet Warren...,' I said, 'Mom, I'm busy!'"
Gates' mother pushed back, however, insisting that Buffett would be interesting and worth her son's time.
"I wasn't convinced," Gates writes in a blog post reflecting on the pair's friendship 25 years later. "'Look, he just buys and sells pieces of paper. That's not real value added. I don't think we'd have much in common,' I told her."
Eventually his mom convinced him to go. "I agreed to stay for no more than two hours before getting back to work at Microsoft," he writes.
But once Gates and Buffett finally got a chance to talk, things just clicked. Buffett pressed the tech mogul with difficult questions about Microsoft, and Gates welcomed the challenge. "These were amazingly good questions that nobody had ever asked," he writes.
Gates abandoned his plan to fly back to work that night. "We were suddenly lost in conversation and hours and hours slipped by. He didn't come across as a big shot investor. He had this modest way of talking about what he does. He was funny, but what impressed me most was how clearly he thought about the world."
After that night, the pair quickly became close. "It began a really unbelievable friendship for me and I could tell that even though we came from different directions, the kinds of things that fascinated us and that we thought were important were very much the same," says Gates, speaking to UNL students.
As friends, the billionaires regularly discuss industry trends and bounce ideas off each other. They agree that who you decide to be friends with can make an impact on your career.
"You will move in the direction of the people that you associate with," according to Buffett, who gave the advice to a group of students at Columbia University. "It's important to associate with people that are better than yourself."
But the true lesson here? "Listen to your mother," Buffett says.
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