# Discrete Mathematics - Intro to Statistical Math

• Apr 9th 2013, 02:30 AM
rtrumpow
Discrete Mathematics - Intro to Statistical Math
I need assistance in writing/answering using the proper text for Discrete Math/Statistical Math. Here is the problem:

A building supplies store carries metal, wood, and plastic moldings. Metal and wood moldings comes in two different colors. Plastic moldings comes in six different colors.

a.) How many choices of molding does this store offer?
On the first glance, I would have answered 3; however, I am assuming they are counting each color as well. I know metal=2, wood=2, and plastic=6. Making this 2+2+6=10

b.) If each kind and each color of molding comes in four different lengths, how many choices does the consumer have in the purchase of one piece of molding?
Metal=1(color)x4(lengths)+1(color)x4(lengths)=8 choices (long version)
Wood=2(color)x4(lengths)=8 choices
Plastic=6(color)x4(lengths)=24 choices

8+8+24=40 total choices
• Apr 9th 2013, 02:51 AM
emakarov
Re: Discrete Mathematics - Intro to Statistical Math
Correct.
• Apr 9th 2013, 05:27 AM
rtrumpow
Re: Discrete Mathematics - Intro to Statistical Math
Quote:

Originally Posted by emakarov
Correct.

How do I write this in proper format such as |B n A|, etc.
• Apr 9th 2013, 07:30 AM
emakarov
Re: Discrete Mathematics - Intro to Statistical Math
Quote:

Originally Posted by rtrumpow
How do I write this in proper format such as |B n A|, etc.

If you are asking how to write mathematical symbols, then see this post. Or are you asking how to write your solution more formally?
• Apr 9th 2013, 01:09 PM
rtrumpow
Re: Discrete Mathematics - Intro to Statistical Math
More formally.
• Apr 9th 2013, 01:57 PM
emakarov
Re: Discrete Mathematics - Intro to Statistical Math
Quote:

Originally Posted by rtrumpow
More formally.

Well, this totally depends on the requirements of the course. There is no one way to write this more formally. In fact, it would not help readability if the proof in the OP is written in symbols.

But you could declare, for example, the following notations. Let M = {m1, m2}, W = {w1, w2} and P = {p1, ..., p6} where mi, wi and pi are the metal, wood and plastic moldings, respectively, of color i. Obviously, |M| = |W| = 2 and |W| = 6. Also, these sets are pairwise disjoint. Question a) asks to find |M ∪ W ∪ P| = |M| + |W| + |P|. Question b) asks to find |(M ∪ W ∪ P) x {1, 2, 3, 4}| where the second factor is the set of lengths.