## Task 3 - 150523

When a pioneer group reported on their trips taken over the past few years, the following was revealed:

(1) Exactly 13 members of this group have been to the Baltic Sea.

(2) Exactly 15 pioneers have been to the Harz.

(3) Exactly 6 pioneers have been to both the Baltic Sea and the Harz.

(4) Exactly 4 pioneers have never been to either the Baltic Sea or the Harz.

Determine the total number of pioneers who belong to this group!
According to (1), exactly 13 of the pioneers had already been to the Baltic Sea.

According to (2) and (3), the number of pioneers who had already been to the Harz but not yet to the Baltic Sea was $15-6=9$, so exactly 9 pioneers. Therefore, due to $13+9=22$, exactly 22 pioneers of this group had already been to at least one of the mentioned vacation spots.

According to (4) and since all the present pioneers were accounted for; the number of them was $22+4=26$.