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

August 31, 2021 | education

| **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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