Find the perimeter of triangle ABC if BC is twice as long as AC AB = 2cm 8mm AC is 9mm shorter than AB.

According to the condition of the problem, it is specified that the side AB = 2 cm 8 mm, the side AC is 9 mm shorter than the side AB, and the side BC is twice as long as the side AC, therefore:

1) 2 cm 8 mm – 9 mm = 28 mm – 9 mm = 19 mm = 1 cm 9 mm – the length of the speaker side;

2) 1 cm 9 mm * 2 = 19 mm * 2 = 38 mm = 3 cm 8 mm – the length of the BC side;

The perimeter is the sum of all the sides of the triangle.

3) 2 cm 8 mm + 1 cm 9 mm + 3 cm 8 mm = 28 mm + 19 mm + 38 mm = 85 mm = 8 cm 5 mm – the perimeter of the triangle ABC.

Answer: 8 cm 5 mm perimeter of triangle ABC.