Yes, he could give each and every person $10.50 and have nothing - and we'd still have needy and homeless people all over the world
900 million people live under the global poverty line of $1.90 a day.
That is 1.71 billion dollars a day to lift the entire planet out of poverty.
The fact alone that one person could do that for a month and still have more money left over than he can spend in a lifetime just boggles the mind.
If you further assume that most of these people don't have nothing, they just have less than $1.90 it becomes more crazy. My old statistics professor said that if you have no information, assume the average. So let's assume it takes 95 cents on average to bring someone just above the poverty line. That means Bill Gates alone could lift the entire planet out of poverty for three months before his fortune runs out.
While that shows how little these crazy fortunes are in global contexts, it also shows how crazy rich these people are compared to everyone else. It means the richest top ten could end poverty for a year and still be rich. Can you even imagine what it could mean to the poor of the world to not be poor for a year? How many of them would use the opportunity to secure a better future? At the end of that year, many of the poor would not go back to being poor. Millions would be permanently enabled to have a better life.
I applaud Melanie Gates to convince Bill to use a good part of his fortune like this, even if there's a lot of shady deals involved that the future will judge (largely, the crowding out of other organisations that try to help).
But the real problem is not that this money could be used to feed the poor. The real problem is that this money, if it had not been taken by the super-rich, would circulate much faster within the economy and would create more wealth. After the "trickle down" bullshit, a number of real economists have done the checking and they all come to the conclusion that money given to the rich hurts the economy while money given to the average people stimulates it.
Or in other words: In Bill Gates hands, these are 78 billion. In the hands of ordinary people, this would be 90, 100 or more billions. That is the real damage the super-rich do to all of us.