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ELI5 Yahaaa

Counting without losing your place

Why Count in Groups of Five?

Tally marks group by five so you never have to recount from the beginning.

Four upright strokesA fifth struck acrossthemEach bundle is worthfiveCount the bundles, notthe marks
Five at a time, so you never lose your place.

  1. Step 1 of 5

    Counting live is easy to lose track of.

    A long row of marks Recount from the startMarks in bundles Just count the bundles

    Recording passing cars or votes as they happen means you cannot pause. One distraction and you have no idea where you had got to.

  2. Step 2 of 5

    Each mark is made as the thing happens.

    11Somethinghappens2+Make one stroke3 Forget thetotal entirely

    You never hold a running total in your head. One event, one stroke, which means the count survives any interruption.

  3. Step 3 of 5

    The fifth mark is drawn across the group.

    Four uprightstrokesOne struckacrossA closed bundleof five

    Four upright strokes and then a diagonal through them closes the bundle. The shape is instantly recognisable as a group of five.

  4. Step 4 of 5

    Adding up becomes counting in fives.

    Counting 37 marksslow anderror-proneCounting 7 bundlesquick andreliable

    Instead of counting thirty-seven separate marks you count seven bundles and two strays, which is far quicker and far harder to get wrong.

  5. Step 5 of 5

    Five suits hands and eyes alike.

    Groups of fivematches onehandRecognised as a shapeno countingneededEasy to add upfive, ten,fifteen

    Five matches the fingers on a hand, and a bundle of five is small enough to recognise as a shape without counting its parts.

    Tally marks are among the oldest maths we know of, cut into bone tens of thousands of years before writing existed.

The short version

Tally marks group counts into fives so you record one event at a time and add up bundles instead of recounting everything.

Try it yourself

Tally passing cars for five minutes without bundling, then with bundles. The bundled sheet is far quicker to total.

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