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

A.

it is a scalene triangle

B.

it is right angled isosceles triangle

C.

it is an equilateral triangle

D.

It is an isosceles triangle but not right angled

Correct answer is C

(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 + 10o = 50o + 10o = 60o

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

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

Hence, it is an equilateral triangle