Question

A collage in the shape of a regular pentagon is mounted on a rectangular frame as shown below.
What is the value of x?
A. 72

B. 18

C. 20

D. 36

Answer 1

Well, you could first calculate the size of one interior angle of the pentagon.
Total of interiors = (no.of.sides-2)180 = (5-2)180 = 540
Size of one interior angle = 540/5 = 108
So that angle on the bottom left within the grey region = 108.
So its supplementary angle is 180-108=72
So you now have a triangle with angles x, 72 and 90.
I'm sure you can finish off.

Answer 2

@allank so its 72?

Answer 3

No, you are looking for the value of x. And it is one of the angles in a triangle with the other angles being 72 and 90. So what is the value of x?
Hint: angles in a triangle add up to 180

Answer 4

b

Answer 5

well, thank you!

Answer 6

Yes. You're welcome :)