Question

In Fig. 11.16, find the sum of 1, 2, 3, 4, 5, 6, 7, 8 and 9​

Answer 1

Since all the angles contribute to make a pentagon … the sum of the angles will be 540

Answer 2

Answer:

540°

Step-by-step explanation:

There are two methods for this

Method 1

ABC, ACD and ADE are triangles. Therefore, the sum of the interior angles of a triangle is 180°

That means,

1 + 2 + 3 = 180°

4+ 5 + 6 = 180°

7 + 8 + 9 = 180°

Then 1 + 2 + 3 + 4 + 5 +6 + 7 + 8 + 9 = 180° + 180° +180° = 540°

Method 2

As we can see that this is a pentagon, we can find the sum of the angles by using the formula to find the sum of the interior angles of a polygon

180° x (n-2)) where n is the number of sides in the polygon

In this the number of sides is 5

Then 180° x (n-2) = 180° x (5-2) = 180° x 3 = 540°

Hope it helps