Question

18. Two angles of a triangle are in the ratio 4:5. If the sum of these angles is equal to the thi
angle, find the angles of the triangle.
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Answer 1

Let the two angles of the triangle be 4x and 5x. 

Then, as per the question, we know

third angle =4x+5x=9x

We know that sum of all the angles of a triangle is 180∘.

∴4x+5x+9x=180°⇒18x=180°⇒x=10°   ....[On dividing both sides by 18]

So, first angle = 4x∘ = 4×10︋°=40°,

second angle = 5x° = 5×10°=50° and

and third angle = 9x∘ = 9×10°=90°