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avatar+26 

Zinc has a density of 0.258 lb/in³ (pounds per cubic inch).   

Darius is making a pyramid out of solid zinc.  The pyramid has a square base 5 inches on each side, and a height of 3.3 inches.   

How many pounds of zinc does he need? 

Show all your work.  Do not round the final answer.  

 Jan 31, 2019
 #1
avatar+27470 
+3

Have a look at  http://mdk12.msde.maryland.gov/instruction/curriculum/hsa/geometry/math_reference_sheet.html  to see the formulae for calculating the volume of various shapes (including a square based pyramid).  

 

For this question note that mass = density*volume.

 Jan 31, 2019
 #2
avatar+26 
0

I'm sorry but I don't understand but thank you for your help

BellaNight7310  Jan 31, 2019
 #3
avatar+27470 
+4

ok.  Volume of square based pyramid is V = (1/3)*base area*height

 

Here base area = 5^2 in2

height = 3.3"

 

Hence V = (1/3)*25*3.3  in3

 

So mass = V*density = (1/3)*25*3.3 in* 0.258 lb/in3 → (1/3)*25*3.3*0.258 lb

 

I'll leave you to do the multiplication.

 Jan 31, 2019
 #4
avatar+26 
+1

ok thank you so much

BellaNight7310  Jan 31, 2019

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