The angles of triangle are (x + 10)°, (2x - 40)° and (3x - 90)°.

MATHEMATICS

WAEC 2009

The angles of triangle are (x + 10)°, (2x - 40)° and (3x - 90)°. Which of the following accurately describes the triangle?

A. it is a scalene triangle
B. it is right angled isosceles triangle
C. t is an equilateral triangle
D. It is an isosceles triangle but not right angled

Correct Answer: C. t is an equilateral triangle

Explanation

(x + 10)^o + (2x - 40)^o + (3x - 90)^o = 180

6x - 120 = 180

6x = 180 + 120

6x = 300

x = \(\frac{300}{6}\)

x = 50

x + 10^o = 50^o + 10^o = 60^o

2x - 40 = 2(50^o) - 40 = 60^o

3x - 90 = 3(50^o) - 90^o = 60^o

Hence, it is an equilateral triangle

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