Counting 2

The first instance of  is under the Probability and statistics Math Mission. This exercise plays with some of the counting techniques.

Types of Problems
There are three types of problems in this exercise:


 * 1) Combination: This problem has a selection from a group of objects where order is not relevant. The student is asked to fid out how many possibilities there are in the situation.Count2-1.png
 * 2) Multiplication principle: This problem has a situation described where multiple selection are needed. The student is asked to find the number of total possibilities.Count2-2.png
 * 3) Arithmetic sequence: This problem describes a person counting from a certain number by a certain amount. The student is asked to find the number that the counter will stop on.Count2-3.png

Strategies
This exercise is easy to get accuracy and speed badges because although the numbers change, the problems themselves are very consistent in their difficulty. You just need to learn how to do the three types.


 * 1) The Combination problem seems to always be handshakes. If it is, a combination where you choose two can be performed by taking the given number of people, subtracting one, multiplying those numbers together, and dividing by two.
 * 2) The multiplication principle means to take the possible outcomes for each part of the event, and multiply those numbers together for the total number of possibilities.
 * 3) For the Arithmetic sequence problem you can use arithmetic sequences from pre-calculus. In other words, take the first number and add the product of the difference between numbers and one less than the term that you want.