The angles of a heptagon (a shape with 7 sides) are supposed to add up to 900 degrees, so just add up all the sides that you know and subtract it from 900 and you will have x! Do the same thing with the second one, except is is a hexagon and all the angles should add up to 720 degrees. (Don't forget to add the right angle, which is 90 degrees) So add up all the sides you know and subtract from 720 to get x.
The amount of aluminum in square meters needed to make the mailboxes = 1863(surface area of each mailbox)
Surface area of each mail box = ½(surface area of cylinder) + (Surface area of rectangular prism/box - area of the surface of the box that joins the half-cylinder)
✔️Surface area of ½-cylinder = ½[2πr(h + r)]
r = ½(0.4) = 0.2 m
h = 0.6 m
π = 3.14
Surface area of ½-cylinder = ½[2*3.14*0.2(0.6 + 0.2]
= 0.628(0.8)
Surface area of ½-cylinder = 0.5024 m²
✔️Surface area of the rectangular box/prism = 2(LW + LH + WH)
L = 0.6 m
W = 0.4 m
H = 0.55 m
Surface area = 2(0.6*0.4 + 0.6*0.55 + 0.4*0.55)
Surface area of rectangular box = 1.58 m²
✔️Area of the surface joining the half cylinder and the box = L*W = 0.6*0.4 = 0.24 m²
✅Surface area of 1 mailbox = (0.5024) + (1.58 - 0.24)
= 0.5024 + 1.34
= 1.8424
Amount of aluminum needed to make 1863 mailboxes = 1863 × 1.8424 = 3,432.3912
