Ondra, Matěj, and Kuba received the following toys from their grandparents for Christmas: a large fire truck, a remote-controlled helicopter, and a Merkur construction set. Their cousin Petr told at home:

"Ondra got the large fire truck. Kuba wished for it, but he didn't get it. Matěj doesn't like construction sets, so the Merkur wasn't for him."

It turned out that in his statement about who got which gift or didn't get it, Petr was wrong twice and only once told the truth. So, how did it really go with the gifts?

(M. Volfová)

Idea. First, find out who got the fire truck.
Petrov's statements about the boys are:

1. Ondra got the fire truck,
2. Kuba did not get the fire truck,
3. Matěj did not get the Merkur.

If Ondra had received the fire truck, the first two statements would be true. But only one statement is supposed to be true, so Ondra could not have received the fire truck.

If Matěj had received the fire truck, two statements would again be true, namely the second and third, and that is not possible.

Therefore, the fire truck must have been received by Kuba. The first and second statements are thus false, and the third must be true, that Matěj did not get the Merkur. Matěj did not get the fire truck either (which Kuba received), so he must have received the helicopter.

The gifts were distributed as follows: Kuba got the fire truck, Matěj the helicopter, and Ondra the Merkur.

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