More fun Math help, please :)

[Ucinrus]

How many layers will your cake have?
5
What is the radius of the top layer?
6
What is the radius of the bottom layer?
14
How much cake in cross-sectional area does each guest need?
4.5
Your cake will feed 374 guests.

When I work this out I get 376 as the answer for guests. I cant figure out if its rounding or not(Ive rounded up, down, left, right, wont work) so I've come here since I got a nice response last time.

How I came to get my answer.
n = (rb-rt)/(layers-1);
n=2 in this case, so after I find the area of each circle, add 2 for the next layer.

Area = (PI)(r^2)Constant I am using is 3.141592654
Do this 5 times for each layer until r=14. Then Divide by 4.5 for each piece of cake a person wants. 1692/4.5 = 376=/=374.....
Thanks in advance

Note:the cases I used are from the assingment I recieved, and I do not believe its a spelling error for the final.

[smartAXE]

you shouldn't/can't round UP when you cant have fractions of something, ie: this cake will feed 45.6 people.
my guess would be parts of the cake not being used cause of the cross section needed, try it with each individual layer then add them up
hopefully its not a small typo, those are the worst

[Ucinrus]

How did you calculate 45.6 as the total amount fed?

[Porcell]

Are you assuming the layers are 6, 8, 10, 12, and 14? Because it doesn't say that, and you usually don't assume things in a math problem.

Area = (3.14159)*(6² + 8² + 10² + 12² + 14²)
Area = (3.14159)*(36 + 64 + 100 + 144 + 196)
Area = (3.14159)*(540)
Area = 1696.45 units²

Each person needs 4.5 units² of cake. So 1696.45 / 4.5 = 376.99 people

[Ucinrus]

Well I didnt Assume, theres something called this http://en.wikipedia.org/wiki/Arithmetic_progression. So I was given 6 as the top and 14 as the bottom and found out 2 was the amount it grew/reduced. But then yes, you also got the same answer as me and it must be something that was said in class with a variable being changed or such.... : / Ty though.


Edit, that came off as sounding harsh at first, so not intended! D:

[silentk59]

You see heres your problem, I see someones trying to do this equation with the unit of measurement PI, and your trying to serve cake.

Clearly the physics of the new two, pie and cake, dont match or give correct numbers. =P

[Porcell]

My statement stands. Unless there is something in the problem that states that the layers of the cake follow an arithmetic progression, or you are specifically working on an arithmetic progression chapter, it is incorrect to assume that to be the case. The cake could just as easily, logically, be 14, 14, 10, 10, 6.

I found the problem. The problem is that you need to calculate each layer on it's own, and divide each layer by 4.5. This is because you can't smash together all the left over fractions and get a serve-able piece of cake.

Quick copy/paste of the problem in excel.

Pi     Radius   Divisor (pi*Rad^2/Divisor)
3.14149	6	4.5	25.13	= 25 pieces
3.14149	8	4.5	44.67	= 44 pieces
3.14149	10	4.5	69.81	= 69 pieces
3.14149	12	4.5	100.52  = 100 pieces
3.14149	14	4.5	136.82  = 136 pieces
				
			Sum =	374 pieces

[Ucinrus]

My statement stands. Unless there is something in the problem that states that the layers of the cake follow an arithmetic progression, or you are specifically working on an arithmetic progression chapter, it is incorrect to assume that to be the case. The cake could just as easily, logically, be 14, 14, 10, 10, 6.

I found the problem. The problem is that you need to calculate each layer on it's own, and divide each layer by 4.5. This is because you can't smash together all the left over fractions and get a serve-able piece of cake.



OMG I love you, Thank you Thank you Thank you Thank you
Quick copy/paste of the problem in excel.

Pi     Radius   Divisor (pi*Rad^2/Divisor)
3.14149	6	4.5	25.13	= 25 pieces
3.14149	8	4.5	44.67	= 44 pieces
3.14149	10	4.5	69.81	= 69 pieces
3.14149	12	4.5	100.52  = 100 pieces
3.14149	14	4.5	136.82  = 136 pieces
				
			Sum =	374 pieces

OMG I love you, Thank you Thank you Thank you Thank you