Deductive Reasoning

Which statement is a valid conclusion based on the argument?
If a polygon is a regular pentagon, then the polygon has exactly five congruent angles.
The polygon is a regular pentagon.

• Therefore, the polygon is a rectangle.
• Therefore, the polygon is a regular quadrilateral.
• Therefore, the polygon has exactly five congruent angles.
• Therefore, the polygon has congruent sides.

Tags

CCSS.8.G.A.2

(1) If you drive safely, then the life you save may be your own.
(2) AJ drives safely.
(3)  The life AJ saves may be his own.
Is statement (3) logical given the Law of Detachment, Syllogism, Contrapositive, or is it invalid?

• Law of Detachment
• Law of Syllogism
• Law of Contrapositive
• invalid

p→q
q→r
∴p→r
Which law is modeled?

• Law of Syllogism
• Law of Detachment
• Law of Contrapositive
• Law of Shannon

Use Law of Syllogism to make a conclusion.
 If a number is divisible by 10, then it is divisible by 2.  If a number is divisible by 2, then it is even.

• If a number is divisible by 10, then it is even,
• If a number is even, then it is divisible by 10.
• If a number is divisible by 2, then it is even.
• If a number is even, then it is divisible by 2.

Using the Law of Detachment, what can you conclude?
If x has a value of 4, then 2x has a value of 8.
The value of x is 4.

• x = 4
• no conclusion can be made
• 2x does not have a value of 8
• 2x has a value of 8

Tags

CCSS.8.EE.C.7

Use Law of Syllogism to make a conclusion.
If the perimeter of a square is 20 ft, then the length of a side is 5 ft.
If the length of a side of a square is 5 ft, then the area is 25 ft².

• If the side of a square is 5 ft, then the perimeter is 20 ft.
• If the perimeter of a square is 20 ft, then the area is 25 ft²
• If the area of a square is 25 ft², then the side length is 5 ft. 
• If the are of a square is 25 ft², then the perimeter is 20 ft.

Tags

CCSS.HSA.REI.A.1

Write the if-then statement that follows from the pair of true statements. If the sun is shining, then it is a beautiful day.  If it is a beautiful day, then we will have a picnic.

• If the sun is shining, then it is a beautiful day.
• If it is a beautiful day, then the sun is shining.
• If the sun is shining, then we will go on a picnic.
• If we go on a picnic, then the sun is shining.

If there is lightening, then it is not safe to be out in the open. Mary sees lightening from her home.

• It is not safe for the lightening

• No conclusion can be made.

• It is not safe for Marty to be out in the open.

• There is lightening.

Tags

CCSS.RI.11-12.2

CCSS.RI.8.1

CCSS.RI.9-10.1

CCSS.RL.8.1

CCSS.RL.9-10.1

What conclusion can be drawn from the following statements?
If Todd goes to the movies, then Sarah will go to the movies.  
If Chris goes to the movies, then Todd will go to the movies.

• If Chris goes to the movies, then Sarah will go to the movies.
• If Todd goes to the movies, then Chris will go to the movies.
• If Sarah goes to the movies, then Chris will go to the movies.
• If Chris goes to the movies, then Todd will go to the movies.

__________________________ uses specific observations to make generalizations.

• Deductive reasoning
• Inductive reasoning