Sets and SubsetsDate: 23 Jan 1995 14:45:14 -0500 From: Xin Li Subject: Sets and Subsets In my algebra 1 class, my teacher talked about sets and subsets. You might wonder why I asked problems about SIN and COS and now I'm back on the basics. Well, I learn from two math books. One covers that kind of stuff and another covers the basics. I'm only in 7th grade, and my dad wants me to learn ahead so he teaches me stuff on that book while I have to keep up with work from my math class. Anyway, my teacher talks about Sets and Subsets. She said that integers are a subset of reals, and whole numbers are a subset of integers, and counting numbers are a subset of whole numbers, and so on and so forth. What does that mean? I'm having a test on that tomorrow, so if you could help me to get this info down today, I'll be forever grateful. Thanks. Date: 23 Jan 1995 21:51:38 -0500 From: Dr. Sydney Subject: Re: Sets and Subsets Dear Xin, Hello, again! You asked a good question about sets and subsets. When we say a set (let's call it A) is a subset of another subset (let's call it B), that means that every element that is in A is also in B. For instance, the counting numbers (this is the set: {1, 2, 3, ...}) is a subset of the whole numbers (this is the set {0, 1, 2,...}, I think!). This is because every element in the set of counting numbers is also in the set of whole numbers. 1, 2, 3, ... are all whole numbers. Does that make sense? Similarly the whole numbers are a subset of the integers because every element of the set of whole numbers is also in the set of integers (that is the set {...-2, -1, 0, 1, 2, ...}). Do you see? I hope this helps. Write back if you have any more questions. --Sydney, dr. math Date: 24 Jan 1995 17:27:54 -0500 From: Xin Li Subject: Sets and Subsets Yeah, I think I get it now. Suppose we say in bag A, there are 10 apples and in bag B there are 10 apples and 10 oranges, then we could say that bag A is a subset of bag B because bag B has everything bag A has. Is that what it means? Date: 24 Jan 1995 18:09:31 -0500 From: Dr. Sydney (Sydney Foster) Subject: Re: Sets and Subsets Dear Xin, Yes, that is it! Good example. If you have any other problems, write us back! --Sydney, Dr. Math From: Dr. Steve (Steve Weimar) Subject: Sets and Subsets Dear Xin, It looks as though you do have the idea, although it might be more accurate to imagine that bag A has ten apples and in bag B there are ten oranges AND bag A. Then the fruit in bag A could be described as a subset of the fruit in bag B. -- Dr. Steve |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994- The Math Forum at NCTM. All rights reserved.
http://mathforum.org/dr.math/