December 10, 200619 yr Ok, I'm pretty sure I got this right, but I'm not doing so well in math (comparatively, that is, it's my only lowish B and my dad will flip...) and he has a wierd way of grading that he only chooses about 4 or 5 problems to grade, so I don't wanna get a 75% for missing one of these . Sob story being over... ~ Using pi = 3 [i think he's lazy], Michael calculated that the cost for painting the roof of a cylindrical water tower would be $36. If this is true, how much would it cost to paint around the outside? Height = 8 ft. Radius = 6 ft. I got $864 which doesn't seem right, yet I've double-checked it 3 times... :-k Then part b... ~ How much water could you put in the tower? I got 864 cubic ft., same as part a... :-k Any help would be greatly appreciated :pray: Owner of quest cape since December of 2006
December 10, 200619 yr Doh, look @ the posts below me for answer to first Q. But, I did get 864 cubic feet of water.
December 10, 200619 yr Diminshed, I think you forgot to use pi (3) when calculating the area of the circle. ----------------------------------- a) How much would it cost to paint around the outside? Given: Cost for painting top of cylindrical tower = $36 Pi = 3 Radius = 6 ft Height = 8 ft If the radius is 6 ft, then the area (A=pi*r^2) of the top is 3*(6^2) = 108 sq. ft. Thus it costs $1 to paint every 3 sq feet. So to find the cost of painting the outside, you need to find the surface area of the cylindrical tower. I'm assuming that this surface area does not include the bottom of the tower because you can't really paint something that's attached to the ground. To find the area of the cylindrical tower's side, multiply the 'base' (the circumferance of the tower's base/top = pi*2r = 3*2*6 = 36) by the height of the cylinderical tower. 36 * 8 = 288 sq. ft. I'll assume that the roof isn't painted yet so just add the area of the root to the side and multiply by 3 to get the cost. (288+108)/3 = $132. If the roof is already painted, just do 288/3. B) How much water could you put in the tower? Just find the volume of the cylinder. In this case volume = area of the top multiplied by the height. 108 * 8 = 864 cubic ft of water. Think my math is right - I hope :P
December 10, 200619 yr Diminshed, I think you forgot to use pi (3) when calculating the area of the circle. ----------------------------------- a) How much would it cost to paint around the outside? Given: Cost for painting top of cylindrical tower = $36 Pi = 3 Radius = 6 ft Height = 8 ft If the radius is 6 ft, then the area (A=pi*r^2) of the top is 3*(6^2) = 108 sq. ft. Thus it costs $1 to paint every 3 sq feet. So to find the cost of painting the outside, you need to find the surface area of the cylindrical tower. I'm assuming that this surface area does not include the bottom of the tower b/c you can't really paint something that's attached to the ground. To find the area of the cylindrical tower's side, multiply the 'base' (the circumferance of the tower's base/top = pi*2r = 3*2*6 = 36) by the height of the cylinderical tower. 36 * 8 = 288 sq. ft. I'll assume that the roof isn't painted yet so just add the area of the root to the side and multiply by 3 to get the cost. 3*(288+108) = $1188. If the roof is already painted, just do 3*288. B) How much water could you put in the tower? Just find the volume of the cylinder. In this case volume = area of the top multiplied by the height. 108 * 8 = 864 cubic ft of water. Think my math is right - I hope :P actually it would mean $1/3 for every square feet, since it's $36/108, not the other way around. so 1/3*(288+108)=$132
December 10, 200619 yr For the SA: Area of the top+Area of the side+Possibly the Area of the bottom Area of the top: Pi*r^2=3*6^2=3*36=108 Area of the side: Circumference of the top*Height. The circumference - 2r*Pi=2*6*3=12*3=36 Height - 8 8*36=288 288+108=396 396/3=132 If you don't need the top, it's 288/3, or 96. Cenin pân nîd, istan pân nîd, dan nin ú-cenich, nin ú-istach.Ithil luin eria vi menel caran...Tîn dan delu.
December 10, 200619 yr actually it would mean $1/3 for every square feet, since it's $36/108, not the other way around. so 1/3*(288+108)=$132 Hehe, thanks for catching that :-). Stupid me =P
December 10, 200619 yr Author Thanks so much everybody :D The math seems to work out right, and it makes logical sense. Thanks for helping double check someone else's homework when most people wouldn't even do their own :XD: Oh, and just so you all don't feel like you helped someone cheat, I forced myself to endure the numbers to see why it was what it was, too : Owner of quest cape since December of 2006
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