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Best Guess · Puzzle #26 · Sunday, October 25

Best Guess: the answers

Four questions, each with one true number. Here they are with their answers, how to reason each one out, and where the number comes from. Play today's Best Guess.

  1. 1. How many students were enrolled in US public schools (pre-K through 12th grade) in fall 2022?

    The answer: about 49.6 million. They were taught by about 3.2 million full-time-equivalent public school teachers.

    Napkin math
    1. 330Mpeople in the US
    2. ÷80years a lifetime
    3. ×13grades from kindergarten to 12th

    ≈53.6Mstudents

    The true figure is about 49.6 million students (National Center for Education Statistics). On a napkin, take 330 million people in the US, divided by 80 years a lifetime, times 13 grades from kindergarten to 12th, and you get about 54 million students. The estimate is 1.1 times too high, close enough to score 9.7 out of 10. The target is wider than it looks: every guess between 25 million students and 99 million students scores at least 7.0.

    Source: National Center for Education Statistics, Fast Facts: Back-to-School Statistics

  2. 2. How many fans in all went to the matches of the 2026 FIFA World Cup in the US, Canada and Mexico?

    The answer: about 6.8 million. That nearly doubled the old record of 3.59 million, set at the 1994 World Cup, also in the US.

    Napkin math
    1. 100matches in the tournament
    2. ×60kfans a match

    ≈6Mfans

    The real answer is about 6.8 million fans (Yahoo Sports). Without looking anything up, take 100 matches in the tournament, times 60,000 fans a match, and you get about 6 million fans. The estimate is 1.1 times too low, close enough to score 9.4 out of 10. The target is wider than it looks: every guess between 3.4 million fans and 14 million fans scores at least 7.0.

    Source: Yahoo Sports, Total record-breaking attendance numbers revealed for 2026 World Cup

  3. 3. How many pounds of fresh bananas did Americans eat in 2021?

    The answer: about 8.9 billion. Bananas are the most-eaten fresh fruit in the US, ahead of apples.

    Napkin math
    1. 330Mpeople in the US
    2. ×104bananas each a year (two a week)
    3. ÷3bananas to a pound

    ≈11.4Bpounds

    The real answer is about 8.9 billion pounds (USDA Economic Research Service). Without looking anything up, take 330 million people in the US, times 104 bananas each a year (two a week), divided by 3 bananas to a pound, and you get about 11 billion pounds. It's 1.3 times too high, which as a guess would still have scored 8.9 out of 10. The target is wider than it looks: every guess between 4.5 billion pounds and 18 billion pounds scores at least 7.0.

    Source: USDA Economic Research Service, Food Availability (Per Capita) Data System: Fruit (fresh)

  4. 4. On average, how many teeth does a US adult aged 20 to 64 still have?

    The answer: about 26. A full adult set is 32, so the typical working-age adult has lost about 6 to wisdom teeth, decay or gum disease.

    Napkin math
    1. 32teeth in a full adult set
    2. −4teeth wisdom teeth taken out

    ≈28teeth

    The true figure is about 26 teeth (National Institute of Dental and Craniofacial Research). Without looking anything up, take 32 teeth in a full adult set, minus 4 wisdom teeth taken out, and you get about 28 teeth. It's 1.1 times too high, which as a guess would still have scored 9.7 out of 10. Because only the ratio counts, anything between 13 teeth and 52 teeth was worth 7.0 or more.

    Source: National Institute of Dental and Craniofacial Research (NIH), Tooth Loss in Adults (Age 20 to 64)

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