Explanation
We know, by angle sum property, the sum of angles of a quadrilateral is 360o. The given angles are ∠A=90o,∠B=6x−5o,∠C=7x−15o,∠D=2x+5o.
Then, ∠A+∠B+∠C+∠D=360o
⟹ 90o+6x−5o+7x−15o+2x+5o=360o
⟹ 15x+75o=360o
⟹ 15x=360o−75o=285o
⟹ x=19o.
Therefore, option B is correct.
Given ratio of angles of quadrilateral ABCD is 1:2:3:4.
Let the angles of quadrilateral ABCD be 1x,2x,3x,4x, respectively.
We know, by angle sum property, the sum of angles of a quadrilateral is 360o.
⇒1x+2x+3x+4x=360o
⇒10x=360o
∴x=36o.
∴∠A=1x=1×36o=36o,
∠B=2x=2×36o=72o,
∠C=3x=3×36o=108o
and ∠D=4x=4×36o=144o.
∴ The largest angle =144o.
Hence, option D is correct.
Given the two angles are 60o and 40o.
Also, the other two angles are in the ratio 8:5.
Let the angles be 8x,5x, respectively.
⇒60o+40o+8x+5x=360o
⇒100o+13x=360o
⇒13x=360o−100o
⇒13x=260o
∴x=20o.
∴8x=8×20o=160o,
and 5x=5×20o=100o.
∴ Tmeasure of other two angles are 160o and $$100^o.
Hence, options B and C are correct.
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