Question

16) The three angles of a triangle are 11x – 1,4x + 15 and 20x – 9. Find the measure of all the angles of the triangle. *

a) 55, 35,92
b) 54,35,91
c) 56,32,78
d) 66,33,91*
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Answer 1

1st∠ = 11x - 1

2nd∠ = 4x + 15

3rd ∠ = 20x - 9

as we know that sumof all angle of triangle = 180°

so ,

(20x - 9) + (11x - 1) + (4x + 15) = 180

20x - 9 + 11x - 1 + 4x + 15 = 180

20x + 11x + 4x = 180 + 9 + 1 - 15

35x = 180 - 5

35x = 175

x = 175 / 35

x = 5

1st∠ = 11x - 1

= 11 × 5 - 1

= 55 - 1

= 54°

2nd∠ = 4x + 15

= 4 × 5 + 15

= 20 + 15

= 35°

3rd ∠ = 20x - 9

= 20 × 5 - 9

= 100 - 9

= 91°

Option 'B' is correct .