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The False Diary (illustration)
FILE No.51Unsolved

The False Diary

Difficulty ★☆☆about 5 minEveryday MysteriesComparing a story to factsWeather and plans
A boy writes a false diary entry and a classmate immediately calls it a lie. Compare it with the evidence.

Case Record

Monday. Kohei, a sixth-grader, forgot to write his homework diary and wrote it early in the classroom.

Kohei had played video games all day yesterday and did not remember it, so he lied. He wrote: "Yesterday was Sunday. I spent all day with my little brother. In the morning we played catch at the nearby park. At noon we played at the arcade in front of the station. In the evening we played video games together at home."

A classmate who came in looked at the diary and said right away, "That’s a lie."

Your question

Why was it exposed as a lie? Compare the evidence with the diary.

Case Files

Evidence

Diagram

Diary vs. factsItemDiaryFactBrotherWith Kohei all dayAt soccer practice, 9-5WeatherNot mentionedClear all dayPark, arcadeWentBoth openWhere was the brother?
Diagram

Hints

If you get stuck, open the hints one at a time, in order.

Open hint 1

Compare the “with my brother” parts of the diary with the evidence.

Open hint 2

Check what his brother does on Sundays.

Open hint 3

What happens to that plan in yesterday’s weather?

Solve It

Your question

Why was it exposed as a lie? Compare the evidence with the diary.

Choose the answer closest to the truth.

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The Truth

It was clear yesterday and his brother practiced at the field from morning to evening

The answer is “it was clear yesterday and his brother practiced at the field from morning to evening.”

His brother belongs to a soccer club in the city and practices outdoors from 9 a.m. to 5 p.m. on Sundays. Practice is canceled in rain, but yesterday was clear from morning to night, and practice went ahead as planned. So during the morning and noon when the diary says the brother was with him at the park and arcade, he was actually at the field. The arcade and park were both open yesterday, so “closed” and “under construction” are no reasons. Whether the brothers get along is something the classmate cannot know.

Why it was a lieBrother practices Sundays 9 to 5Clear weather: no cancellationPractice was held as plannedAnswer: he was at the field all day
Diagram of the solution

Key Points

  • Compare the diary with yesterday’s facts
  • Events that depend on weather
  • Match the evidence to the diary

Why people get fooled

You doubt places and times in the diary and do not check the brother’s schedule.

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