Answer:
C
X=-16
Step-by-step explanation:
Use the formula that states that the sum of the angles of an n-sided polygon is given by
S=(n−2)180
0
........(1)
Since we are given that the two angles are right angles and each of the remaining angles is 144
0
, therefore, the sum is:
S=90
0
+90
0
+(n−2)144
0
.........(2)
Therefore setting (2) equal to (1) we get
(n−2)180
0
=90
0
+90
0
+(n−2)144
0
⇒(n−2)180
0
−(n−2)144
0
=180
0
⇒(n−2)(180
0
−144
0
)=180
0
⇒(n−2)(36
0
)=180
0
⇒n−2=
36
180
⇒n−2=5
⇒n=5+2=7
Hence, the polygon has 7 sides.
C) 225m
Explanation:
Looking at the board we see each side is 25m in length. Each side has 5 squares, therefore the length of one side of each square is 5m (25m/5=5).
Let’s count how many full squares there are. There’s 5 completely full squares (one in the middle, and one on each of the four edges).
There’s also half-full squares which we COULD calculate separately using the area of a triangle. However, we know that two halves make one full square so let’s count how many full blocks these make up. There’s 8 triangles (or half full squares), therefore there are 4 full squares.
Adding this to the clearly full blocks shows 4+5=9. There are 9 fully shaded squares. The area of a square is A=s x s (Area = length of side x length of side). Therefore, one square’s area is 5x5=25m^2. The area of 9 squares is 25 x 9 = 225m^2.
Therefore the answer is C
