I think there's an easy way and a hard way to do this, and I think that the way I'm about to describe is the easier way.
Probability = (number of successful outcomes)/(total number of possible outcomes)
<em>How many total pairs can be drawn from 8 total pens ?</em> -- The first one drawn can be any one of 8 pens. For each of these . . . -- The second one drawn can be any one of the remaining 7 . -- Total number of ways of drawing a pair = (8 x 7) = 56 ways. -- But there aren't 56 different different pairs. Whether you draw A and then B, or B and then A, you wind up with the same pair. There are 2 different ways to draw each pair, so the 56 ways of drawing a pair only produces <u>28</u> different pairs.
<u>How many pairs are two of the same color ?</u>
<em>Possible number of blue pairs:</em> The reasoning is exactly the same as calculating the TOTAL number of pairs, as explained above. With 5 blue pens, you can make <u>10</u> different pairs. AB, AC, AD, AE, BC, BD, BE, CD, CE, and DE.
<em>Possible number of red pairs:</em> The reasoning is exactly the same as calculating the TOTAL number of pairs, as explained above. With 3 red pens, you can make <u>3</u> different pairs. AB, AC, and BC.
Total number of possible same-color pairs = 10 + 3 = 13
successes / total possible outcomes = 13/28 = <u>46.4</u>% (rounded)
A perpendicular bisector of a line segment 'l' is a line that is perpendicular to the line segment 'l' and cuts the line segment 'l' into two equal parts.
Given:
1. A triangle WXY.
2. A perpendicular bisector from vertex W that intersects XY at point Z.
Conclusion based on the drawing:
a. Z is the midpoint of the line segment XY because point Z lies on the perpendicular bisector of XY.