Question

Q21. The third angle of a triangle if two angles are 90° and 60°

30°
40°
60°
70°​

Answer 1

Step-by-step explanation:

We know that the sum of the interior angles of a triangle is 180∘. Let third angle in all the given triangles be x∘. Therefore,

(i) 38∘+100∘+x∘=180∘

    x∘=180∘−138∘

    x∘=42∘

(ii) 116∘+30∘+x∘=180∘

    x∘=180∘−146∘

    x∘=34∘

(iii) 80∘+40∘+x∘=180∘

    x∘=180∘−120∘

    x∘=60∘

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Answer 2

Answer:

(A) 30°

Step-by-step explanation:

Let the unknown angle be x°.

90°+60°+x° = 180° [Angle sum property]

=>150°+x° = 180°

=>x° = 180°-150°

=>x° = 30°