Elementary Test Prep: Math 4 Test (Grades 3-4)Understand compound statements using or.

Lesson Page Mathematical Reasoning

OR	In logic, two statements can be combined to form a compound statement using the word "or". The compound statement using "or" is true when either or both statements (or facts) are true.

Logic is the study of reasoning, and it deals with statements that are either true or false. 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 statement.

The compound statement using "or" is true when both statements (or facts) are true, or one of the statements (or facts) are true.
	A circle is 4 round. (true)
	A hexagon has 6 sides. (true)
A circle is round or a hexagon has 6 sides. (true) (T + T) = True
The compound statement using "or" is true when one or both statements (or facts) are true.
	A circle is round. (true)
	A hexagon has 4 sides. (false)
A circle is round or a hexagon has 4 sides. (true) (T + F) = true
The compound statement using "or" is false when both statements (or facts) are false.
	A circle is not round. (false)
	A hexagon has 4 sides. (false)
A circle is not round or a hexagon has 4 sides. (false) (F + F) = false

Examples:

1. A dog is an animal (true) or 5 + 5 = 10 (true).
(T + T = T)

Since both facts are true, the entire sentence is true.

2. A dime is a coin (true) or a dime is worth 25 cents (false).
(T + F = T)

Since the first fact is true, the entire sentence is true.

3. 8 - 5 = 6 (false) or a bird is a cat (false).

(F + F = F)

Since both facts are false, the entire sentence is false.

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

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