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In a triangle ABC, ∠A = x°, ∠B = y° and ∠C = (y + 20)°. If 4x – y = 10, then the triangle is :
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- Right-angle
- Obtuse-angled
- Equilateral
- None of these
Correct Option: A
Given :- ∠A = x° , ∠B = y° , ∠C = ( y + 20 )° and 4x – y = 10
We know that , ∠A + ∠B + ∠C = 180°
⇒ x + y + ( y + 20 ) = 180°
⇒ x + 2y = 180 - 20 = 160° ........... ( ⅰ )
4x – y = 10 ........... ( ⅱ )
From ( ⅰ ) and ( ⅱ ) , we get
⇒ y = 70 , x = 20
∴ The angles of the triangle are 20° , 70° , 90° .
Hence , the triangle will be Right-angle triangle .
