Container Height and Volume
Date: 08/01/97 at 16:17:09 From: Ashley Hemingway Subject: Volume problem How in the world do you solve this problem? A container's height is increased by 4 cm, and the length and width remain the same. If this change increased the volume by 12 percent, what was the original height of the container? I would like to tell you how much Dr. Math has helped me to mature and grow in the field of mathematics. Thank you. Yours truly, Ashley Hemingway :)
Date: 08/01/97 at 18:34:39 From: Doctor Mike Subject: Re: Volume problem Thanks for the kind words about our help in the past. I'll try to keep up the good work. From the way the problem is stated, I assume the container is box- shaped, so the volume is the product of length and width and height. Let the three original values be L, W, and H. Then the original volume is L*W*H. The new volume is L*W*(H+4), but it also equals the original volume times 1.12 since it has 12 percent more volume. So you get the equation L*W*(H+4) = L*W*H*1.12 which you can solve for H. First divide both sides of the equation by L*W to get an equation with H as the only variable. Note that L*W is the area "B" of the base of the box. The problem would be worked in essentially the same way if it were stated that "A container's height is increased by 4 cm, and the base remains exactly the same." Then the equation is B*(H+4) = B*H*1.12 and you proceed in the same way. You don't really need to know anything about the shape of the bases. They could both be squares, or both be circles, or both be equilateral triangles, or whatever. What I did in the previous paragraph is to make this problem just a little more general, but keep the idea of how to solve it the same. Your increased maturity will help you to "look at the bigger picture" like this. The situation could be made even more general by changing the problem from "the base remains exactly the same" to "the area of the base remains exactly the same". The first container could be a rectangular-based box and the second container a circular-based can, but if both of them have the same AREA then we can still use the equation B*(H+4) = B*H*1.12 where B is that common area. I hope this helps. If you have more questions, write back to us. -Doctor Mike, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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