The sides of the triangle are 5: 7: 11, and the sum of the largest and smallest sides is 80 cm.

The sides of the triangle are 5: 7: 11, and the sum of the largest and smallest sides is 80 cm. Calculate the perimeter of the triangle.

The task is in parts. We take one part for x, then
1 side – 5x
2 side – 7x
3rd side – 11x
The largest side is 11x, and the smallest is 5x, their sum is 80 cm.
Let’s make the equation 11x + 5x = 80
We solve it 16x = 80; x = 80: 16; x = 5
Find the lengths of the sides of the triangle
1 side 5x = 5 * 5 = 25 (cm)
2 side 7x = 7 * 5 = 35 (cm)
3 side 11x = 11 * 5 = 55 (cm)
Find the perimeter of the triangle (P is the sum of the lengths of all sides of the triangle) P = 25 + 35 + 55 = 115 (cm)
Answer. 115 cm