Remember: Not one keeper, but many copies that agree: trust comes from the crowd. Ask a grown-up about the risks of any new kind of money.
Read and answer
Read the story first, then answer.
Kettle Hollow keeps its copiesIn the made-up village of Kettle Hollow, people traded with little tokens, and someone had to keep count of who owned how many. Mira kept a notebook and wrote down each payment, like "Tess gives Leo two tokens." Everyone trusted her. Then rain soaked the notebook, the pages smudged, and nobody agreed who owned what. So the village tried something new: everyone kept their own copy. Each payment was called out to all, and everyone wrote it down. One day Leo secretly changed his copy to say he had more tokens. When the villagers compared, four copies agreed and one did not, so the village followed the most copies and Leo's change was ignored. To make cheating harder still, the pages were linked in a chain. Each page carried the seal of the page before it. This idea is real. In 2008, someone using a made-up name described it and called the new money Bitcoin. The first computers joined in 2009.
1
What went wrong with Mira's notebook of who owned what?
Mira ran out of tokensLeo bought the notebookRain soaked it, so nobody agreed who owned what
2
Leo changes his copy. The other four copies agree. Which story does the village follow?
Leo's story, since he changed it lastThe story the most copies agree onMira's story, since she was the keeper
3
Each sealed page carries the of the page before it.
sealbanktoken
4
If someone changes an old page, every seal after it breaks.
TrueFalse
5
There are 5 copies. Look at the table. With 3 copies changed, copies are still true.
Order, match and fix
6
Number the steps of Kettle Hollow's story.
Leo changes his copy and is ignored
Mira keeps one notebook
Rain smudges the pages
Everyone keeps a copy
7
Join each word to what it means in the story.
1keeper
2copy
3seal
4cheat
Aone person who writes the record
Blinks a page to the one before
Ca record each villager has
Dchanges a record in secret
8
Circle every true sentence about this new idea.
There is no bank in the middleOne king owns the recordMany computers keep copiesAnyone can print as many coins as they likeOnly twenty-one million coins can ever exist
9
The idea was described in . The first computers joined a year later, in 2009.
10
Tess says: a cheat only needs to change one copy to win. Is Tess right?
YesNo
11
Why is it hard for one cheat to win here?
The cheat must change most of the copies at once, while others watchThe cheat is not allowed to writeOnly a bank can write
12
In your own words, why do many copies that agree make cheating harder?
13
Draw five notebooks in a row. Color the one that Leo changed.
Scan the code at the top to mark this sheet on screenTake a photo of your answers or type them. It is marked for you automatically, and your score is kept.
Answer key · Set A
The birth of Bitcoin
1Rain soaked it, so nobody agreed who owned what The pages smudged in the rain and nobody agreed who owned how many tokens. One keeper's notebook can be lost, soaked or changed.
2The story the most copies agree on When copies disagree, the village follows the most copies: four against one.
3seal The pages are linked in a chain, each one carrying the seal of the page before.
4True A changed old page undoes every later seal, so tricks show up fast.
52 5 − 3 = 2. Now 3 copies say the new story, so most copies agree on it.
64, 1, 2, 3 One keeper first, then the soaked notebook, then everyone's copies, and last the cheat who is outvoted.
71-A, 2-C, 3-B, 4-D A keeper writes alone, copies are shared, a seal links pages, and a cheat changes things in secret.
8There is no bank in the middle, Many computers keep copies, Only twenty-one million coins can ever exist Nobody owns the record and nobody can print more: the limit is twenty-one million coins, with many computers keeping copies.
92008 The idea was described in 2008, and the first computers joined in 2009.
10No A cheat must change most copies at once, and the others notice.
11The cheat must change most of the copies at once, while others watch Trust comes from the crowd, not one person: many copies that agree keep each other honest.
12Your own words: a grown-up reads it.
Mark each answer, count the right ones and write the score on the sheet.