# The sum of the two sides of the triangle is 72dm, the third side is 18dm, less than the sum

The sum of the two sides of the triangle is 72dm, the third side is 18dm, less than the sum of the two sides, find the perimeter of the triangle.

Given: a triangle with sides a, b, c; a + b = 72 dm; c is 18 dm less than a + b.

Find: the perimeter of the triangle R.

Solution: the perimeter of a triangle is the sum of the lengths of the sides of the triangle, which is calculated by the formula P = a + b + c. From this formula, we know the sum of the lengths of the sides a and b (a + b), we need to find the length of the side c.

P = a + b + c = 72 dm + c = 72 dm + 54 dm = 126 dm.

c = (a + b) – 18 dm = 72 dm – 18 dm = 54 dm.

Answer: 126 decimetres perimeter of the triangle

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