Task 4 - 120624 Manfred reported in the Circle of Young Mathematicians about a visit to the Rostock Overseas Harbor:

"I saw a total of 21 ships from five different countries there. The number of ships from the GDR was half as large as that of all the foreign ships lying in the harbor. These came from the Soviet Union, the People's Republic of Bulgaria, Finland, and India.

The number of Soviet ships was two more than that of the Bulgarian ships, which in turn was one more than that of the Finnish ships, which finally was two more than that of the Indian ships."

Determine the number of ships from the GDR, the Soviet Union, the People's Republic of Bulgaria, Finland, and India that Manfred saw in Rostock!
The number of ships based in the GDR is $\frac{1}{3}$ of the total number, according to the problem, so 7 ships came from the GDR. The remaining 14 ships came from the other four countries.

Now, according to the problem, Manfred has seen at least 1 Indian ship, and consequently at least 3 Finnish, 4 Bulgarian, and 6 Soviet ships. Since this already adds up to 14 ships, the required numbers are found.

Solutions of the 2nd Round 1972 adopted from [5]

### 3.14 XIII. Olympiad 1973

### 3.14.1 1st Round 1973, Class 6