Who Broke the Promise

Difficulty ★★☆about 6 minContradictory TestimonyHonest accountsPaths of information

The teacher’s vase broke and she found out, though none of the four told on him. How did it reach her?

Case Record

At a school with only six pupils in all, Ms. Kawakami’s precious vase was broken. Taichi broke it. On the way home he talked it over with four friends, Ken, Daisuke, Mayu and Riho, and asked them: "Please don’t tell the teacher."

The next day Taichi was called in by the teacher and scolded about the vase. All four say they did not mean to tell on him.

Your question

If the four accounts are true, how could it have reached Ms. Kawakami? Look closely at the evidence.

Case Files

Evidence

E-1SchoolSix pupils in all: Taichi, Ken, Daisuke, Mayu, Riho and Chinatsu.
E-2The four accountsKen: After we parted I forgot about the vase and told no one. / Daisuke: I told my father, but he told no one. / Mayu: I told my mother. / Riho: I told Chinatsu by phone, but Chinatsu told no one.
E-3Confirmed factsNo one else overheard the talk on the way home after Taichi asked the four. When each of the four told their person, no one else overheard.

Diagram

Hints

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

Open hint 1

Can a story reach someone even if you did not mean to tell on anyone?

Open hint 2

Check in order whom the four told and what they told.

Open hint 3

Think of the case where it reaches the person without anyone passing it on.

Solve It

Your question

If the four accounts are true, how could it have reached Ms. Kawakami? Look closely at the evidence.

Choose the answer closest to the truth.

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The Truth

The person they told was Ms. Kawakami herself

The answer is “the person they told was Ms. Kawakami herself.”

In fact, Mayu’s mother is Ms. Kawakami. Mayu did not mean to tell on anyone to a teacher at school; she was telling her mother about the day at home. But the mother who heard it was Ms. Kawakami herself. The teacher could learn the circumstances without anyone passing it on. Ken told no one afterward. Daisuke’s father and Chinatsu did not tell anyone, and no one else heard the talk on the way home. This puzzle does not ask you to establish who is whose parent from the text alone. Here, think of the circumstance in which “did not mean to tell on him” is not the same as “it did not reach her.”

Diagram of the solution

Key Points

Check the routes in order
Notice another way to refer to the same person
Assume everyone is honest

Why people get fooled

Hearing “did not mean to tell on him,” you assume nothing reached the teacher.

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