Pre-Algebra: Chapter 6-6
Measures of Central Tendency (or mode, median and mean!)
When we have data to play with, we want to first organize it. Place the series of numbers in order from small to large. The mode of a data set is the number of items that appear most often. You CAN have more than 1 mode.
The median of a data set is the number in the middle when they are in order IF there are ODD numbers of values. If there are EVEN numbers of data, then the median will lie between 2 values. Average (or find the mean, see below) these 2 and you have the median.
The mean (or average) is the sum of the data divided by the number of pieces of data. See these examples for clarity!
Algebra: Chapter 9-5
Inequalities in 2 variables
Given an inequality, treat it as an equality and using the x and y intercepts, find the solution to the equality. Plot it on your graph paper. If the inequality is just <, or >, then the boundary line (the line you draw connecting the dots) will itself be dotted or dashed. This mean that the points on the line are NOT part of the solution. If the inequality has a ≤ or ≥, then the line will be solid, signifying that the line is part of the solution.
There are 2 ½ planes on the graph, one side of the boundary line that belongs to the solution set (this side will be shaded as part of the solution) and the other side of the line that does not satisfy the inequality.
Now to figure out what ½ plane to shade, pick a point [I like to pick (0, 0) or (1, 1)] and try those (x, y) values in the inequality. IF the point chosen makes the inequality TRUE, then shade that part of the plane. IF the point chosen does not satisfy the inequality, then shade the OPPOSITE side ½ plane.
The textbook is actually pretty good in this area, see pages 417-419 for good examples.