Question

Two angles of a polygon are right angles and the remaining are 120 degree each find the number of sides in it. ANS: 5

Answer 1

Let n be the number of sides.

∴ Sum of angles = 2*90° + (n - 2)*120°

⇒ Sum = 180° + 120n - 240

We know sum of all angles of a polygon is - 180°(n-2)

∴ 180n - 360° = 180° + 120n - 240

⇒ 180n - 120n = 180 - 240 + 360

⇒ 60n = -60 + 360

⇒ 60n = 300

⇒ n = 300/60

or, n = 5

Hence answer is 5. The polygon is a Pentagon.

Hope this helps you.

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Answer 2

Answer:

Step-by-step explanation:

Let number of sides of polygon is n.

Two angles of a polygon are right angles and the remaining are 120 each

Sum of total angles of a polygon is = 180 (n−2)

n= number of sides of polygon

Now,

2×90°+(n−2)×120° = (2n−4)×90°

180°+120n-240°=180n-360°

180n-120n=180°+360°-240°

60n=300°

n=5°