Ballpark

143 estimation questions in 7 packs. Nobody knows these numbers. The game is how close you can get.

Pick your packs

143 questions in the packs you picked. 5 a round.

How to play

  1. 1Pick your packs. All of them are on to start with.
  2. 2Read the question and make a guess. Nobody knows these numbers, which is the point.
  3. 3Type it the way you would say it: 48000, 48k or 2.5 million.
  4. 4Lock it in. The line shows where you landed, and the stamp shows where you should have.
  5. 5Read the napkin math under it, then go again. Five questions make a round.

How to get close to a number nobody knows

The instinct with a question like these is to reach for a number, any number, and type it. Almost everybody does it on their first round, and it is why first rounds score badly. A number pulled out of the air is usually wrong by ten times or more, and on this scoring that is worth nothing at all.

What works is breaking the question into pieces you can each guess. You may not know how many times a heart beats in a day, but you know it beats about seventy times a minute at rest, and that a day has 1,440 minutes. Multiply them and you are at about a hundred thousand, which is right. Every piece was a guess and the answer still lands, because small errors in separate pieces partly cancel out instead of piling up.

Decide how many digits the answer has before you decide the first one. Is it thousands, millions or billions? That choice is most of the score. A guess of 40,000 against an answer of 48,400 scores 91. A guess of 400,000 is the same instinct with one zero too many, and it scores nothing.

The mistake groups make is anchoring. Whoever speaks first sets the number everybody else adjusts from, and the adjustments are always too small. If you are playing round one phone, everyone writes a guess down before anyone says one out loud. It feels like an exam for ten seconds, and it is the difference between a room full of guesses and one guess with decoration.

One house rule worth adopting: argue after, not before. Once the stamp lands, the closest player explains how they got there. That is where the game teaches something, and by the third round people are multiplying out loud before they type.

Is this the same as a Fermi problem?

Yes, and that is where the idea comes from. Enrico Fermi, the physicist, was famous for estimating things nobody could measure on the spot, and the question physics teachers still use to explain it is how many piano tuners work in Chicago. At the first atomic test he dropped scraps of paper as the blast wave passed and estimated its strength from how far they drifted. He came within about a factor of two of the measured figure, with a handful of paper.

It is not The Price Is Right, where the closest guess without going over wins. Going over costs nothing extra here, and neither does going under. Double and half are scored as the same miss, because in estimation they are the same mistake.

Why double still scores half

A quiz question is right or wrong. An estimate cannot work that way, because nobody is ever exactly right, and a game that only paid exact answers would pay nobody. So Ballpark scores how many times off you were: within 10% is 100 points, double or half is 50, and ten times off is nothing.

The line in the reveal counts the same way. Each mark is ten times the one before it, so a guess twice too big sits the same distance from the stamp whether the answer is forty or forty billion. On an ordinary ruler, every sensible guess for a big number would be squashed into one pixel at the left-hand end.

Common questions

How is Ballpark scored?
By how many times off you were. Within 10% of the answer scores 100. Double or half scores 50. Ten times off scores nothing. Too high and too low are treated the same, because guessing double and guessing half are the same size of mistake.
Where do the answers come from?
Every answer is checked against a source, which is linked under the napkin math along with the year the figure is true for. Where the real number is an average or a range, the answer is the middle of it, and the napkin math says so.
Can I type 48k or 2.5 million?
Yes. Type it the way you would say it: 48000, 48,000, 48k and 48 thousand all work. On a phone the number keyboard cannot type words, so there are thousand, million and billion buttons under the box, and the line beneath reads your guess back in words before you lock it in.
What is napkin math?
Rough arithmetic with round numbers, the kind you could do on a napkin or the back of an envelope. It is how you get close to a number you have never looked up, and every answer here comes with one line of it so you can see how you might have got there.
How long is a round?
Five questions, which takes about three minutes. Five more deals questions you have not seen yet until the packs you picked run out.
Is it any good for a classroom?
It is one of the better maths lessons hiding in a game. Breaking a question into pieces, multiplying rough figures and thinking in powers of ten are all on the curriculum, and a class arguing about whether there are more or fewer than a million of something is a class doing it.

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