Which one of the following sentences shows the mistake Mr Stead has made?

Matt and Yash play chess together every day at lunch. They are at around the same skill level, and they have each won around half of the matches they’ve played against each other.

Mr Stead: “I can’t remember how many games Matt and Yash played last week, but I know Matt won five, so they must have played about ten games.”

Which one of the following sentences shows the mistake Mr Stead has made?

It doesn’t matter who wins, because the important thing is that they both have fun. Matt and Yash may have had lots of homework last week. The players have each won around half, not exactly half, of their games. Either Matt or Yash might have played unusually well last week.

Are you sure you want to leave?

Which one of the following sentences shows the mistake Mr Stead has made?