Question

In triangle​ ABC, the size of angle B is 5 times the size of angle​ A, and the size of angle C is 11 degrees less than 4 times the size of angle A.

Find the size of the angles.

Answer 1

A = 19.1°

B = 95.5°

C = 65.4°

Explanation:

B = 5A

C = 4A-11

We know that a triangle has a total of 180° so:

180 = A + B + C

Which can be written as:

180 = A + (5A) + (4A - 11)

180 = 10A - 11

10A = 191

A = 19.1°

With A, we can work out B and C:

B = 5(19.1)

B = 95.5°

C = 4(19.1) - 11

C = 76.4 - 11

C = 65.4°