Question

I'm sure this is easy and i'm just an idiot.

A triangle has two angle measures of 20 degrees and 30 degrees. Find the third angle. This triangle is a(n) ________ triangle

A) Acute
B) obtuse
C) Right
D) It does not make a triangle.

Oml just help. ;-; (There is no picture just the question and choices).

Answer 1

B) obtuse

Explanation:

Key skills needed: Triangle measure, Triangle Recognition

1) First we need to find the measure of the 3rd angle, and then we can determine what type of triangle it is.

2) The sum of all the interior angles in a triangle add up to 180 degrees. Let's say x is the measure of the 3rd angle.

This means -->
`20 + 30 + x = 180`

20 + 30 is 50, so -->
`50+ x = 180`

Subtract 50 from both sides and you will get x = 130

This means the 3rd angle measures 130 degrees.

3) Now, we have a triangle with a 20 degree angle, a 30 degree angle, and then a 130 degree angle.

An angle with measure with 130 degrees is an obtuse angle

(Keep in mind that an acute angle has a measure less than 90 degrees, a right angle measures 90 degrees, and an obtuse angle has a measure of more than 90 degrees - 130 is more than 90 so it is obtuse)

4) A triangle with 1 obtuse angle is an obtuse triangle, so Choose B) obtuse!!

Hope you understood and have a nice day!! :D