Question

Craig has a building block in the shape of a rectangular pyramid. A net of which is shown below.

Answer 1

Answer:

the answer is D: 294 sq. cm

Step-by-step explanation:

first you want to split the net into 4 triangles and 1 rectangle

a = 12 cm

b =  6 cm

d = 13 cm

calculate the surface area of the pyramid...

1st find the area of the rectangle base

Rectangle base area

b x a = (6 cm) (12 cm)

= 72 sq. cm

next find the area of the triangle on the left

Left triangle

1/2(b)(d) = 1/2 (6 cm)(13 cm)

= 1/2 (78 sq cm)

= 39 sq. cm

Since all the triangles are congruent (same), you will need to multiply by 2 to get the combined area of the triangle on the left and on the right.

Area of left & right triangles

= 2 (39 sq. cm)

= 78 sq. cm

Find the area of the triangle on the bottom

Bottom triangle area = 1/2 (a)(a)

= 1/2 (12 cm) (12 cm)

= 1/2 (144 sq. cm)

= 72 sq. cm

Since the bottom of the triangle is congruent to the top triangle, multiply that by 2 to get a combined area of the triangle on the bottom and top

Area of top & bottom triangles

2 (72 sq. cm) = 144 sq. cm

Finally...add the area of the 4 triangles to the area of the rectangular base

72 + 78 + 144 = 294 sq. cm