# The perimeter of an isosceles triangle is 20.4 m. Find its sides if the base is 3 m less than the lateral side.

October 18, 2021 | education

| Let’s designate the sides of the triangle (a and b) as x, then the base (c) will be equal to x – 3.

Through the perimeter, we find the length of the side x:

x + x + x – 3 = 20.4;

3x – 3 = 20.4;

3x = 20.4 + 3;

3x = 23.4;

x = 23.4 / 3;

x = 7.8 m.

The sides of the triangle a and b are 7.8 m each.

Find the base with:

c = x – 3 = 7.8 – 3 = 4.8 (m).

Checking: 7.8 + 7.8 + 4.8 = 20.4;

20.4 = 20.4.

Answer: a = 7.8 m, b = 7.8 m, c = 4.8 m.

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