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# Is triangle ABC a right triangle? 1. Angle BAC + angle ACB = 100

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Re: Is triangle ABC a right triangle? 1. Angle BAC + angle ACB = 100 [#permalink]
unraveled wrote:
Is triangle ABC a right triangle?

1) ∠BAC + ∠ACB = 100
2) ∠BAC + ∠ABC = 120

Statement 1 tells us that the third angle in the triangle is 80 degrees, because the three angles add to 180. But one of the two angles in the equation could be 90. Similarly Statement 2 tells us the unmentioned angle is 60 degrees, but one of the two angles in the equation could be 90. Using both Statements, we know we have an 80 and a 60 degree angle in the triangle, so the third angle must be 40 degrees, and the triangle is not a right triangle. So the answer is C.
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Re: Is triangle ABC a right triangle? 1. Angle BAC + angle ACB = 100 [#permalink]
unraveled wrote:
Is triangle ABC a right triangle?

1) ∠BAC + ∠ACB = 100
2) ∠BAC + ∠ABC = 120

None of the equation alone is sufficient

Together they are sufficient(Option C)

Angle ABC + Angle BCA +Angle CAB =180........(3)

(3)-(1),we get Angle ABC=80
(3)-(2),we get Angle ACB=60

Hence triangle ABC is not a right triangle
Re: Is triangle ABC a right triangle? 1. Angle BAC + angle ACB = 100 [#permalink]
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