Question

Ellis is painting wooden fenceposts before putting them in his yard. They are each 5 feet tall and have a diameter of 1 foot. There are 10 fenceposts in all. How much paint will Ellis need to paint all the surfaces of the 10 fenceposts? Use 3.14 for π, and round your answer to the nearest hundredth. Provide an explanation and proof for your answer.

Answer 1

@AZ

Answer 2

so they're cylinders

and we're finding the surface area for one

and multiplying by 10 since there's 10 fenceposts

Answer 3

So 39.3?

Answer 4

SA = (2* pi * radius * height) + 2*pi*(radius)^2

diameter = 1 ft
radius = diameter / 2

so what is the radius?

and height = 5
and use 3.14 for pi

Answer 5

I thought .5 was the radius?

Answer 6

It is!

Answer 7

In which case I already did that all and I got 39.3

Answer 8

This is so much easier when explained

Answer 9

hmm that's after you're multiplying by 10, I guess?

I'm getting a slightly different answer

Answer 10

Ok I put .5 as the radius and 5 as the height, it said the volume was 3.93 and mulitplied by 10 thats 39.3

Answer 11

wait I'm dumb

Answer 12

I was accidentally using r= 0.1 instead of 0.5

Answer 13

But I don't get the same answer as you though

Let's plug in the numbers, radius = 0.5 and height = 5

SA = (2* pi * radius * height) + 2*pi*(radius)^2

SA = (2*3.14*0.5*5) + (2*3.14*0.5*0.5)

SA = ??

Answer 14

Oh

Answer 15

You're solving for surface area...

Answer 16

The default setting is volume

Answer 17

whoops

Answer 18

And now it says 174.36

Answer 19

that makes sense haha

Answer 20

oops be careful that you're doing 0.5 * 0.5

Answer 21

So just times ten

Answer 22

and use 3.14 for pi

Answer 23

Oh wait what?

Answer 24

SA = (2*3.14*0.5*5) + (2*3.14*0.5*0.5)

Answer 25

Ok I kind of just searched up volume of a cylinder to help myself out

Answer 26

surface area***

just use a calculator and plug in the numbers for the first parenthesis

and then the second one

and add

you were on the right track but just forgot the decimal in the radius- 0.5 and not 5

Answer 27

Oh my god

Answer 28

I put 55 instead of 5

Answer 29

*head slap*

Answer 30

ye, I accidentally made a typo 3 times too when calculating it so no worries

Answer 31

And so 172.8

Answer 32

Thats with it multipled by 10

Answer 33

Yup! I got 172.7 but you were probably using the actual value of pi instead of just 3.14

Answer 34

So its rounded up to 172.9

Answer 35

no no

just 172.7 is fine

Answer 36

and the units would be square feet

Answer 37

A=2πrh+2πr2

R= .5

H= 5

A=2πrh+2πr2=2·π·0.5·5+2·π·0.52≈17.27876

SA= 17.28

17.28 times 10 = 

172.8

Answer 38

Does that work?

Answer 39

yeah, except that they want you to use 3.14 for pi

`Use 3.14 for π`

so just say that the final answer is 17.27

and 17.27 * 10 = 172.70

added an extra zero because
`round your answer to the nearest hundredth`

Answer 40

A=2πrh+2πr2

R= .5

H= 5

A=2πrh+2πr2=2·π·0.5·5+2·π·0.52≈17.27876

SA= 17.28

17.27 * 10 = 172.70

Answer 41

yeah I guess that works haha

Answer 42

yay ok, next