Points D, E, F are the midpoints of sides ABC. The perimeter of triangle DEF is 5. Find the perimeter of triangle ABC.

1. A, B, C – the vertices of the triangle. DEF is a triangle formed by the middle lines. DE, EF, DF – middle lines.

2. The middle line of the triangle is equal to half of the side parallel to it. Therefore, AC = 2DE, AB = 2EF, BC = 2ДF.

3. The perimeter of the triangle DEF = DE + EF + DF = 5 centimeters.

4. The perimeter of the triangle ABC = AB + BC + AC.

5. We replace in the last expression AC with 2DE, AB with 2ЕF, BC with 2ДF.

The perimeter of the triangle ABC = 2DE + 2EF + 2DF. = 2 (DE + EF + DF) = 2 x 5 = 10 centimeters.

Answer: The perimeter of triangle ABC is 10 centimeters.



One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.