Question

ABC is an isosceles triangle with a perimeter

of 74 cm. how long is the longest side of this
triangle?
A. 10 cm
B. 17 cm
C. 20 cm
D. 27 cm

Answer 1

• 27 cm

Explanation:

Given

• ABC is isosceles
• The sides are, AB = 3x - 3, AC = 3x - 3 and BC = 2x
• The perimeter is, P = 74 cm

Find the value of x first

Use the perimeter formula

• P = a + b + c, where a, b and c are sides of the triangle

Substitute known values to get the equation

• 3x - 3 + 3x - 3 + 2x = 74
• 8x - 6 = 74
• 8x = 80
• x = 10

Find the sides

• AB = AC = 3*10 - 3 = 27 cm
• BC = 2*10 = 20 cm

As we see the longest side is 27 cm