How Many Liters of Paint Needed for Pyramid?

  • Thread starter Thread starter smartguy_ppl
  • Start date Start date
Click For Summary

Homework Help Overview

The discussion revolves around calculating the amount of paint needed to cover the exposed surface of a pyramid constructed from blocks. The pyramid's base is defined as 100 blocks by 100 blocks, with each layer decreasing in size until reaching a single block at the top. Each block has specific dimensions, and the paint coverage is specified per liter.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore various methods for calculating the surface area, including summing the dimensions of the blocks and considering the exposed surfaces. Questions arise about the correct approach to account for the top and sides of the blocks, as well as the overall surface area calculation.

Discussion Status

There is an ongoing examination of the calculations presented, with some participants questioning the methods used and suggesting corrections. Clarifications are being sought regarding the assumptions made about which surfaces need to be painted and how to accurately calculate the total area.

Contextual Notes

Participants are discussing the need to consider only the exposed surfaces of the blocks, and there are indications of confusion regarding the correct application of formulas and the interpretation of the problem's requirements.

smartguy_ppl
Messages
3
Reaction score
0
The base of the pyramid is 100 blocks by 100 blocks; each successive layer is one less block wide and deep, until the top layer which is simply one block. Each block is 97 cm wide by 97 cm deep by 63 cm tall.

If one liter of paint can coat exactly three square meters, how many liters are required to coat the entire exposed surface of the pyramid? Round up to the nearest liter.

I know what to do but is there a "pattern" that can be used here?

EDIT:
Paint Used For Side of Blocks:
1+2+3...+100
= 5050 x width of 97 x height of 63 x 4 sides of a pyramid
= 123,442,200 cm2 / 10 000
= 12,344.22 m2 / 3
= 4114.74 litres of paint

Paint Used For Top of Blocks:
1+2+3...+100
= (100 x 100) (97 x 97)
= 94090000 cm2 / 10 000
= 9409 m2 / 3
= 3136.33

Total:
4114.74 + 3136.33
= 7251.07
= 7251 L.

Can I have confirmation that this is right? :smile: =)
 
Last edited:
Physics news on Phys.org
What is the sum of squares of first 100 numbers? This gives you total periphery. Multiply it with the width and height. You get total exposed surface area. Convert it into sq.mtr.
 
To cover the top of all blocks.
So what will you see if you are on the plane, which is above the top of the pyramid, and look straight down the pyramid?
You will see a 100 blocks x 100 blocks rectangle, right?
So what is the area of that rectangle? Is it also the area of the top of all blocks you must paint?
Viet Dao,
 
Last edited:
yes you have to paint the sides of the blcok and the top of the block
 
It seems that you got the side of the block correctly, but you got the top of the block incorretly...
First, why are you multiply by 4 (sides of the pyramid)?
And if you calculate like that, you will paint all top of the blocks, not just the ones that are exposed.
Viet Dao,
 
Thank you for that comment. I will correct it.
 
smartguy_ppl said:
...
Paint Used For Top of Blocks:
1+2+3...+100
= (100 x 100) (97 x 97)
= 94090000 cm2 / 10 000
= 9409 m2 / 3
= 3136.33
Yup. Correct.
But you don't need the 1 + 2 + 3 + ... + 100. :smile:
See the bolded part of the quote.
Viet Dao,
 
I am sorry for misguiding.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
Replies
1
Views
9K
Replies
3
Views
6K
  • · Replies 26 ·
Replies
26
Views
23K
Replies
3
Views
3K
Replies
2
Views
3K
  • · Replies 15 ·
Replies
15
Views
7K
Replies
4
Views
5K