Compound Statements Review
lesson
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In the above lessons, you learned Logic is the study of reasoning, and it deals with statements that are either true or false. These statements can be joined by the words: and, or, or not.  When attempting to determine the truth value of a compound statement, first determine the truth value (true or false) of each of the components of the sentence.

Remember a compound statement is formed when two or more ideas are joined in one sentence.

The following are examples of compound statements  with all three connectors:
  1. "1 is an odd number and 2 is an even number."
  2. "15 - 5 = 10 or 10 + 2 = 17."
  3. "It is not true that:
     5 + 3 = 8
    and  4 x 2 = 6."

 

When deciding the truth value of a compound statement, first decide the truth value of each of the components of the sentence. 
 Let's take a look at the examples listed above. 

 1.  Decide the truth value of: "1 is an odd number and 2 is an even number."

"1 is an odd number" (true)
"2 is an even number." (true)

 Replace the truth values for the facts: T and T
 T +  T = T

Answer:  The compound statement is true.

 

2.  Decide the truth value of: "15 - 5 = 10  or 10 +2 = 17."

"15 - 5 = 10" (true)
"10 +2 = 17" (false)

Replace the truth values for the facts: T and F
T (
or) F = T

Answer:  The compound statement is true..

 

3.  Decide the truth value of: "It is not true that: 5 + 3 = 8 and  4 x 2 = 6."

"5 + 3 = 8" (true)
"4 x 2 = 6" (not true)

Replace the truth values for the facts: T and T
T (and) T = T

Answer:  The compound statement is true.

 

Remember:

For a compound statement using "and" to be true, BOTH facts must be true.

The compound statement using "or" is true when both statements (or facts) are true, or one of the statements (or facts) are true.

The negation ("not") will always have the opposite truth value of the original statement. What was TRUE, will become FALSE, or what was FALSE, will become TRUE.

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Created by Carol Carroll  revised by Mary Jane Cowell
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