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 09-Nov-2005, 23:26 #1 Xenus Senior Member   Join Date: Nov 2004 Location: Ohio Posts: 1,259 Math help Math help. I have an issue I am tring to find the height of water rising in a pool. What is the area of a trapizoid expressed by a function of h or hieght I cannot seem to get it. I have (((b1+b2)h)/2)w)
 09-Nov-2005, 23:35 #2 Vadi   Join Date: Apr 2004 Location: Austria Posts: 446 Isn't that A=((a+c)/2)*h ? (a,c ... parallel sides)
09-Nov-2005, 23:38   #3
OpenGL guy
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Posts: 2,291

Quote:
 Originally Posted by Xenus Math help. I have an issue I am tring to find the height of water rising in a pool. What is the area of a trapizoid expressed by a function of h or hieght I cannot seem to get it. I have (((b1+b2)h)/2)w)
What's the "w" for? If you want area of a trapezoid, it's just A = (b1 + b2)*h/2. You have to know b1 and b2 and A to compute h.
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 09-Nov-2005, 23:47 #4 Xenus Senior Member   Join Date: Nov 2004 Location: Ohio Posts: 1,259 I'm trying to find the volume of a trapzoidal swimming pool. w is the width of the pool. If the pool is being filled at a rate of 1.2 cubic feet per minute, how fast is the water level rising when the depth of water is 5 feet? We first need to express the volume of water in the pool as a function of , the depth of water in the pool. We find that Calculus trying to find the rate the water is rising at. b2 is dependant on h and since at when h =7 b2 =24 = 24h=7b2 b2=(24/7)h but it still doesn't appear to be right. got it it is actually 16(12h+6/7h^2) Last edited by Xenus; 10-Nov-2005 at 01:45.
 10-Nov-2005, 02:05 #5 Xenus Senior Member   Join Date: Nov 2004 Location: Ohio Posts: 1,259 Does anyone know how to do realted rates on a clock at 10 o'clock. the minute hand is 5 cm and the hour hand is 3 cm? I get dh/dt=(5(2pi)+3(pi/6)+15sin(-pi/6)(11pi/6))/(5.830951895) Last edited by Xenus; 10-Nov-2005 at 02:16.
10-Nov-2005, 02:08   #6
OpenGL guy
Senior Member

Join Date: Feb 2002
Posts: 2,291

Quote:
 Originally Posted by Xenus I'm trying to find the volume of a trapzoidal swimming pool. w is the width of the pool. If the pool is being filled at a rate of 1.2 cubic feet per minute, how fast is the water level rising when the depth of water is 5 feet? We first need to express the volume of water in the pool as a function of , the depth of water in the pool. We find that Calculus trying to find the rate the water is rising at. b2 is dependant on h and since at when h =7 b2 =24 = 24h=7b2 b2=(24/7)h but it still doesn't appear to be right. got it it is actually 16(12h+6/7h^2)
You didn't give us the full problem! But I don't think your answer is correct as w is not a part of the result. For example, if w = 0.000001 ft, then the level will rise very fast, but if w = 100000 ft then the level will rise very slow.

Unless w is one of those other things you didn't tell us
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10-Nov-2005, 02:14   #7
Xenus
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Join Date: Nov 2004
Location: Ohio
Posts: 1,259

Quote:
 Originally Posted by OpenGL guy You didn't give us the full problem! But I don't think your answer is correct as w is not a part of the result. For example, if w = 0.000001 ft, then the level will rise very fast, but if w = 100000 ft then the level will rise very slow. Unless w is one of those other things you didn't tell us
Oh I know that is right the webwork said so. The width was 16 an the bottom base was 12 the 2 sides were only 6 each and I would of got it faster by using the equal triangle form.

Last edited by Xenus; 10-Nov-2005 at 02:23.

 10-Nov-2005, 02:14 #8 Xenus Senior Member   Join Date: Nov 2004 Location: Ohio Posts: 1,259 Now can you check my last question. Does anyone know how to do realted rates on a clock at 10 o'clock. the minute hand is 5 cm and the hour hand is 3 cm? I get dh/dt=((5)(2pi)+(3)(pi/6)-((2pi)(3)cos(-pi/3))+5(((pi/6)cos(-pi/3))-3sin(-pi/3)(11pi/6)))/(5.830951895) Last edited by Xenus; 10-Nov-2005 at 04:13.
 10-Nov-2005, 04:34 #9 Xenus Senior Member   Join Date: Nov 2004 Location: Ohio Posts: 1,259 If somebody could please help that would be great I've done the prob a million times and find ways to get lots of different answers just messing with the prenthesises but none are right so far. I"ve only got 25 minutes left. Oh well it's two late now and I spent about 8hours getting an 89% on the homework. Last edited by Xenus; 10-Nov-2005 at 04:58.

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