My name is Sierra and today I am going to teach you about combinations and the combination formula.
When using the combination formula, that means that you cannot put back any of the numbers you've already used or in other words it is without replacement. The combination formula is defined as the number of distinct combinations of "r" items selected (without replacement) from pool "n"; items (r < or equal to n) is denoted by: nCr also written as C(n,r). To solve a combination problem you use the formula: n!/ r! (n-r)!.
An example of a combination problem would be if there were 500 tickets to a concert and the first 10 got to be front row and you wanted to know how many different combinations there were. If the order of the 10 people does not matter then we can use the above formula. For this problem the formula would look like 500!/ 10! (500-10)! and then you would use your calculator to multiply it out or leave it as so depending on what the question asked.
Being able to calculate combinations is important because eventually you will face a real life situation where you need to choose a certain amount from the total and you'll want to know all the possible combinations and in order to do so you need to understand the combination formula.
For this specific concept I chose to just explain in and use an example problem rather than use a powerpoint or something more creative because this is a rather straight forward concept and if it is not taught in a very simple way it could become confusing. There really is not a trick to the combination formula besides memorizing it and plugging the values into the formula.
Great job explaining why this concept is important!
ReplyDeleteNice! I liked your example :)
ReplyDeletesierra,
ReplyDeletei like that you used a simple example to explain this complex concept. and i like that you listen in class and used an example that was familiar to you. ;) good luck to you. it was great to have you in my class! =]
professor little