Relations in Real LifeDate: 10/02/2012 at 11:06:31 From: Bethany Subject: How a relation range connects to the real world Hi, In class we are currently learning about relations, functions, domain, range, etc. I know that a relation is just a set of ordered pairs, and a function is just a type of relation. I know that the domain is the set of all the 1st numbers, or in other words, the x-values, and the range is the set of all the 2nd numbers, or in other words, the y-values. I know what these are, and a bit more. I just want to know how they relate to the real world ... maybe with some examples of how they might help us in life, in real life situations, so I can know the material a little better? Can you help me connect mathematical relations with the real world? Thank you! Date: 10/02/2012 at 19:48:43 From: Doctor Ian Subject: Re: How a relation range connects to the real world Hi Bethany, Can you imagine a situation where some inputs are not allowed? For example, you might have a mapping from weight, in ounces, to postage required. Can you have a negative weight for that? No. So that would be a restriction on the domain of the mapping, right? What about a situation where, no matter what input you have, there are some outputs you can't get? For example, you might be mapping engine size to maximum speed. Are there some speeds that can't be attained? We know that nothing can go faster than the speed of light, but we might have a lower limit than that. So this would be a restriction on range, right? The idea of a mapping is very, very general, and goes beyond math. For example, you dial a particular phone number, and you expect a certain person to answer, right? That's a mapping -- from phone number to person. Are there some "numbers" that wouldn't connect to any phone? Sure. Are there some people who don't have a phone? Sure. The fundamental idea behind all this is just realizing that sometimes inputs and outputs won't make sense, and you want to stay aware of that, so you don't get caught treating nonsense as if it's meaningful. That awareness is an important skill to have, even if you never use algebra once you're out of school. Does this help? - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ Date: 11/05/2012 at 09:29:10 From: Bethany Subject: Thank you (How a relation range connects to the real world) Thank you for answering my question. I understand more now. |
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