数式ミステリー㊶『数学者のメモ』Page6～The Missing Dollar

Puzzle Challenge!
The Missing Dollar
There were three travelers.

They found a hotel and asked the owner,
“How much is a room for three people?”
The owner said,
“It is thirty dollars.”

Each traveler paid ten dollars, and they stayed at the hotel.
After some time, the owner remembered that the real price of the room for three people was twenty‑five dollars.
He called a bellboy and said,
“Please give five dollars back to the three travelers.”

The bellboy thought it was hard to share five dollars among three people.
So he secretly put two dollars in his own pocket.
And he gave back one dollar to each traveler, three dollars in total.

Now, let’s check the money.
The three travelers paid 10 dollars each to the owner.
Each traveler got 1 dollar back from the bellboy.
So each of them finally paid 9 dollars.
They paid 27 dollars in total.
9 dollars × 3 = 27 dollars.

Then we add the 2 dollars in the bellboy’s pocket to 27 dollars.
We get 29 dollars.
27 dollars + 2 dollars = 29 dollars.
This is not 30 dollars!

Where did the last 1 dollar go?