Hello and welcome to More or Less. We are the program that gets merry with maths and

saucy with statistics, and I'm Tim Harford. This week, let us tell you the tale of probability.

Probability is something we use all the time. We use it to predict the weather, place bets,

and work out our chances of survival during certain pandemics. But probability hasn't

always been understood. And this is something Jacob Goldstein, the presenter of the US Radio

Show Planet Money, explains in his new book Money, the True Story of a Made Up Thing.

I've been speaking to him about the evolution of what we now know as probability,

and the story starts in the 17th century, in France.

And that was in this correspondence between these two French math geniuses. One was Blaise Pascal,

and the other was Pierre De Fermat. And they were trying to solve this problem that people had

been kicking around for a couple of hundred years by this point, often called the problem of

the points. So the problem of the points is a particular game abandoned halfway through,

right? Yeah, exactly right. So it's a game of chance. So you can think of a really simple

one like a coin toss, right? Say you and I are going to bet on a series of coin flips.

So Jacob, let's put this to the test. We can bet a dollar if you like, but I'm tossing one of

God's clean English pounds. We're going to toss a coin three times, and if I get two heads,

I win, and if you get two tails, you win. Okay, so right, so I'm just going to toss it now.

Okay, heads. So that's great. So I'm ahead. But Jacob, we don't really have time to finish the

game. So I'm ahead. So I win and you owe me a dollar. Wait, no, because I may yet have one.

What Pascal and for my figured out is we actually have to go through and count all of the possible

outcomes and then figure out in what percentage of those outcomes would you have one,

and in what percentage of the outcomes would I have one, and then split the part accordingly?

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