Mathematics usually has the power to make people cry. In Melinda French Gates’ case, it made her laugh, a lot. Not because it was easy for her, or because she was a sharp Duke University graduate, but because of how Bill Gates applied it on his wedding day, no less. The couple tied the knot on January 1, 1994, in a famously secretive wedding, reported to have cost $1 million, held on Lanai, Hawaii, on a golf course overlooking the Pacific. Bill was 38. Melinda was 29. The reception, a sit-down dinner for about 130 guests, had big names in attendance, including billionaire Warren Buffett, Paul Allen, Steve Ballmer, Craig McCaw, Katharine Graham, and Dan Evans.

The Microsoft co-founder reportedly tried his best to keep details from leaking. Accounts said he pulled a serious privacy flex by locking down accommodations for guests, including buying out a hotel’s rooms, hiring all the helicopters on Maui so photographers could not fly over, and deploying a private security force to keep reporters and paparazzi at bay. Still, one cute, pivotal moment from that day has since been revealed by Melinda herself. On an anniversary, she posted a video of their wedding cake-cutting ceremony on Instagram and described the exact second Bill’s instincts kicked in. Asked to cut the cake, a shy, flushed Gates started doing the math to figure out how to slice it evenly for everyone present.

As Melinda wrote, “We told you it was time to cut the cake. You thought that meant you needed to cut a slice for everyone and did some astonishingly quick math to calculate exactly how big each slice should be. This is the moment I realized what was happening, and also the moment you realized that the cake had a cardboard middle and I had forgotten to mention it. I laughed so hard I couldn’t speak. I thought my heart was full that night, but the last 25 years have taught me just how full a heart can get. Happy anniversary.” It is oddly heartwarming to see a man who built a fortune in code and algorithms instinctively turn to numbers, mentally breaking cake into fractions to make sure every guest got an equal slice. Even in a moment built for romance and merriment, the analytical brain never quite clocked out.

And then, as if the cake math was not already unforgettable, Bill reportedly went for the most personal kind of grand gesture. He surprised Melinda with a performance by Willie Nelson, often described as one of her favorite singers. Years later, that detail feels even more meaningful in hindsight, because Melinda has written that “Always on My Mind” was a Willie Nelson song they used to listen to together, the kind of shared soundtrack that lingers long after the party ends.
