Question

Use a formula to find the surface area of the square pyramid.
45 ft2
81 ft2
36 ft2
72 ft2

Answer 1

anyone know how to do this cause its confusing me

Answer 2

To get the surface area, use the formula :
SA = area of base + 4 * area of triangle

Answer 3

so i have to find the area of the base and then plus 4

Answer 4

yes.. area of base + 4 times of area of triangle

Answer 5

Find the area of the base and find the area of one of the sides: you'll add the area of one side 4 times to that of the base.

Answer 6

Area of one side is just the area of the triangle with base 3 ft and height 6 ft. Do you remember the formula for the area of a triangle?

Answer 7

area = length times width right

Answer 8

That's true for the base, which is a rectangle, but not for the sides, which are triangles.

Answer 9

do u 1/2 the sides?

Answer 10

For a triangle, the area = 1/2 * base * height

Answer 11

ah ok so for the base is it just 3 x 6 = and for the sides its 3 x 6 1/2 =

Answer 12

I think you need to take a closer look at that diagram...one of those is not correct.

Answer 13

the base isnt correct?

Answer 14

3 x 3

Answer 15

Yes, the base is 3 on a side, so 3 ft*3 ft = ?

Answer 16

ok so the base would be 9 ft

Answer 17

Close. The number is right, the unit is not.

Answer 18

the side would be 3 x 6 = 18 1/2 that 9 right and ok

Answer 19

wait that didnt make sense the unit?

Answer 20

If you multiply 3 ft * 3 ft you get 3*3* ft*ft, right?

Answer 21

ya so would it be ft squared perhapys cause theirs 2

Answer 22

We are talking area here, and area has dimension [length]^2

Answer 23

No, not because there are 2, but because there are 2 which are multiplied. If we were adding two lengths, there would also be 2, but they are added, so the unit would remain simply [length]. See the difference?

Answer 24

ya thats what i meant i just didnt really explain it lol

Answer 25

so the base is 9 ft squared

Answer 26

Whatever you do with the numbers, you also do with the units. It's a good practice to keep them there throughout the problem rather than tacking them on at the end, because they can help you catch mistakes in setting up the problem. If the units come out wrong, there's a very good chance the answer is wrong.

Answer 27

Yes, the base is 9 ft^2. Each side is 9 ft^2 as well. What is the total surface area?

Answer 28

dont i take 9 x 9 now or do i jsut add them i think its times

Answer 29

well if its times its 81

Answer 30

Surface area = area of base + area of side 1 + area of side 2 + area of side 3 + area of side 4

Answer 31

45 right

Answer 32

As sides 1-4 are identical, you could write it as
surface area = area of base + 4(area of side)

45 ft^2, not 45...

Answer 33

well 45 ft squared

Answer 34

45 is not one of your answer choices :-)

Answer 35

i have a habit of not writing that part

Answer 36

thx for your help i understand how to do this now

Answer 37

That's an excellent habit to shed.

Any questions about what we did along the way?

Answer 38

nope no questions

Answer 39

bai!!!! thx!!!!!!!!!!

Answer 40

What if the thing had 3 sides instead of 4? The base would be a triangle, but a different triangle probably than the sides. What would you do to find the surface area there?

Answer 41

well youd have to 1/2 the base as well

Answer 42

Yeah, I don't mean how would you compute the area of the base, just how would you set up the total surface area? For our 4-sided problem, it was
Surface area = area of base + area of side 1 + area of side 2 + area of side 3 + area of side 4

What would it be for this?

Answer 43

i dont think shes here

Answer 44

she probably had to get off

Answer 45

For our triangular-base pyramid, we would have

surface area = area of base + area of side 1 + area of side 2 + area of side 3

and as all 3 sides are identical, we could also write that as

surface area = area of base + 3*area of side

Just make a good diagram, identify all of the different sides and how to find their respective areas, then add up the pieces. Use a little checkmark on the diagram as you go to indicate that you've added each piece.