One side of the triangle is 7 cm, the other is 5 cm. How many cm is the third side, if the perimeter is 18 cm
June 2, 2021 | education
| In order to find the length of the third side of the triangle, we compose and solve the equation.
The condition says that one side of the triangle is 7 cm long, and the other 5 cm.We also know the perimeter of the triangle – 18 cm.
Let’s use the variable x cm to denote the length of the third side of the triangle.
And the perimeter of a triangle can be found using the following formula:
P = a + b + c;
Substitute all the values and solve the equation:
7 + 5 + x = 18;
12 + x = 18;
x = 18 – 12;
x = 6 cm is the length of the third side of the triangle.
Answer: 6 cm.
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