If the sum of the interior angles of a polygon is $3420°$, how many sides does the polygon have?

• A. $21$
• B. $18$
• C. $20$
• D. $19$

Answer: (A)

Verified step by step guidance

1. Recall the formula for the sum of the interior angles of a polygon with \(n\) sides: \(\text{Sum of interior angles} = (n - 2) \times 180^\circ\).
2. Set up the equation using the given sum of interior angles: \((n - 2) \times 180 = 3420\).
3. Divide both sides of the equation by 180 to isolate \((n - 2)\): \(n - 2 = \frac{3420}{180}\).
4. Calculate the right side to find the value of \((n - 2)\) (do not compute the final number here, just express the step).
5. Add 2 to both sides to solve for \(n\): \(n = \left(\frac{3420}{180}\right) + 2\).