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**Zentralblatt MATH**

**Publications of (and about) Paul Erdös**

**Zbl.No: ** 219.05006

**Autor: ** Erdös, Paul; Purdy, G.

**Title: ** Some extremal problems in geometry (In English)

**Source: ** J. Comb. Theory, Ser. A 10, 246-252 (1971).

**Review: ** The authors investigate several geometrical problems of a combinatorial flavour. Let be given n points in the plane. Then they determine at most 4n^{5/2} triangles which have the same non-zero area. On the other hand one can find n points in the plane which determine cn^{2} log log n triangles having the same non zero area.

Several other related results are proved and many unsolved problems are stated.

**Classif.: ** * 05B25 Finite geometries (combinatorics)

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