Use a substitution strategy to solve the following problem. Two isosceles triangles have the same base length. The equal sides of one of the triangles
are 3 times as long as the equal sides of the other. Find the lengths of the sides of the triangles when
their perimeters are 34 cm and 82 cm.

The length of the equal sides of the isosceles triangle with a perimeter of 34 cm perimeter is 12 cm

The length of the equal sides of the isosceles triangle with a perimeter of 82 cm perimeter is 36 cm

The base length of both triangles is 10 cm

Step-by-step explanation:

The given parameters are;

The base length of the triangles are equal

The base length of one of the triangle = The base length of the other triangle

The equal sides of one of the triangles = 3 × The length of the equal sides of the other

The perimeter of the triangles are; 34 cm and 82 cm

Let 'b' represent the base length of each triangle, let 'a' represent the length of an equal side of the smaller triangle with a perimeter of 34 cm and let 'c' represent the length of an equal side of the larger triangle with a perimeter of 82 cm

For the smaller triangle, we have;

b + 2·a = 34..(1)

For the other triangle;

b + 2·c = 82...(2)

Given that the side length of the larger triangle are larger than those of the smaller triangle, and that the side length of the larger triangle is 3 times the side length of the smaller triangle, we get;

c = 3·a

By the substitution method, from equation (2) we get;

b + 2·c = b + 2 × 3·a = b + 6·a = 82

∴ b + 6·a = 82...(3)

Subtracting equation (1) from equation (3) gives;

b + 6·a - (b + 2·a) = 82 - 34 = 48

b - b + 6·a - 2·a = 48

4·a = 48

a = 48/4 = 12

The length of the equal sides of the 34 cm perimeter (smaller) isosceles triangle, a = 12 cm

From c = 3·a, and a = 12, we get;

c = 3 × 12 = 36

The length of the equal sides of the 82 cm perimeter (larger) isosceles triangle, c = 36 cm

From equation (1), we get;

b + 2·a = 34

∴ b + 2 × 12 = 34

b = 34 - 2 × 12 = 10

The base length of both triangles, b = 10 cm

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