Trapped in a Room

Case Record

At a training facility under renovation, a call for help came from a staff member, Tanaka.

"I went in to get materials and the door handle broke, so I can’t get out. The lights won’t come on and I don’t remember the room number."

Tanaka is in one of rooms A to E, which stand in a straight line. The windows are blocked with construction boards. Before the call was cut off, Tanaka said:

"Since I came in, I heard a piano through the wall. After it stopped, a while later I heard an electric saw through the wall."

The manager checked the day’s work records and the building’s soundproofing test record, and narrowed down the room to rescue.

Your question

Matching the records in the evidence, which room is Tanaka in?

Case Files

Evidence

E-1Room layoutRooms A, B, C, D and E stand in a straight line on one side of the same corridor, in that order. Adjacent rooms share one wall.
E-2Usage record of the dayFrom when Tanaka entered the room until the call: first a piano was played in Room B, then an electric saw was used in Room D. No other playing or saw use in other rooms in this period. No moving of instruments or machines and no playback of recordings.
E-3Soundproofing test recordWith all doors closed, these two kinds of sound are heard only in the source room and the room immediately adjacent that shares a wall. Not heard two or more rooms away. All doors were closed that day.

Diagram

Hints

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

Open hint 1

Consider the two sounds separately rather than at once.

Open hint 2

In which rooms can the piano be heard?

Open hint 3

There is a room common to the candidates from each sound.

Solve It

Your question

Matching the records in the evidence, which room is Tanaka in?

Choose the answer closest to the truth.

Share my result

The Truth

Room C

The answer is “Room C.”

The piano was played only in Room B. According to the test record, that sound can be heard through the wall only in the immediately adjacent rooms, A or C. The power saw was used only in Room D. Under the same conditions, that sound can be heard in C or E. The only room common to the two candidate sets is Room C. Tanaka was trapped in Room C. The key is not how loud or how it seemed, but combining the range the sound reaches in this building with the day’s usage record.

Diagram of the solution