2.4 Deductive Reasoning

Example of Deductive Reasoning
The catalog states that all entering freshmen
must take a mathematics placement test.
Conclusion
:
You will have to take a
mathematics placement test.
You are an entering freshman.
An Example:
2.4 Deductive Reasoning

Inductive or Deductive Reasoning?
Geometry example…
60
◦
x
Triangle sum property –
the sum of the angles of any
triangle is always 180 degrees.
Therefore, angle x = 30°
Deductive Reasoning – conclusion is based on a property
2.4 Deductive Reasoning

Inductive or Deductive Reasoning?
Geometry example…
What comes next?
Colored triangle rotating 90° CW in
the corners of the square
Is there a rule?
Inductive Reasoning
2.4 Deductive Reasoning

2.4 Deductive Reasoning

2.4 Deductive Reasoning

Deductive Reasoning Is…
•
Deductive reasoning is when you start from
things you
assume to be true
, and draw
conclusions that must be true if your
assumptions are true.
For Example
All dogs have a tail.
Buddy is a dog.
Therefore Buddy has a tail.
2.4 Deductive Reasoning

How Can Deductive Reasoning Be Applied In
School?
Math
Scott has a case of soda in his house since there are 13
cans of soda left I deduce that Scott has drank 11 cans of
soda.
English
When I see ‘like’ in a sentence, I deduce that it is a simile.
2.4 Deductive Reasoning

Science
Using laws and rules to make assumptions
The law of gravity means everything that goes up must
come down
I threw a baseball in the air
That means the baseball must come down.