The Mathematics of Love: Patterns, Proofs, and the Search for the Ultimate Equation

by Hannah Fry

Put this list in a spreadsheet, with the name of the group in the first column, and the number of people the group represents in the next. The next step is to decide how likely each group of people is to actually show up if you invite them. Think about how far away people live. What else is going on in their lives? Do they secretly hate you? You get the idea. Think in terms of a percentage but write it down as a decimal. For example, your close friend from home and her boyfriend might be 95 percent likely to attend, so they would collectively get a score of 0.95. This makes up the third column of your spreadsheet. Multiplying the second column—the number of people in each group—by their score in the third column gives you a fourth column containing the “expected” number of people who will RSVP with a yes. As you go down the list, from the VIPs to the also-rans, keep a running total of the expected number of guests in the fifth column. The simplest method is then to set the cutoff once the running total of expected guests exceeds the capacity of the venue. By doing this you will, on average, invite the right number of people to your wedding. The table on the following page gives you an example of how the bottom end of this spreadsheet might look. With a venue that can host one hundred guests, you should invite everyone up to Gordon and family. You’ll send out invitations to more than one hundred guests, but on average you can expect only one hundred to arrive. Unfortunately...