G.4C verify that a conjecture is false using a counterexample

If an animal is furry, then it is a hamster. What would be an appropriate counterexample?

• goldfish
• frog
• elephant
• cat

Tags

CCSS.HSS.CP.A.5

The product of two negative numbers is greater than the sum of the two numbers. What is an appropriate counterexample?

• -3 and -3
• True. There is no counterexample
• -1 and -1
• 4 and 6

Tags

CCSS.7.NS.A.2A

CCSS.7.NS.A.2B

If it is an angle, then it is acute. What is an appropriate counterexample?

• 70⁰
• 45⁰
• 120⁰
• True. There is no counterexample.

Tags

CCSS.7.G.B.5

True or False: a counterexample is an example that makes a definition or conjecture incorrect

• True
• False

How can you prove a conjecture is false?

• Counterexample
• Not Possible
• Patterns

Determine if this conjecture is true. If not, give a counterexample.
The difference of two negative numbers is a negative number.

• true
• false; -11 - (-13)  = 2
• false; -7 - (-5) = 2
• false; -19 - (-17)

Tags

CCSS.6.NS.C.5

Which is a counterexample of: If a four sided shape has two sides the same length, then it must be a rectangle.

• quadrilateral
• rectangle
• square
• triangle

Tags

CCSS.4.G.A.2

If it is a line, then it has a positive slope. What is an appropriate counterexample?

• y = -4x
• y = 6x
• y = 1/5x + 5
• y = 2x - 6

Tags

CCSS.8.EE.B.5

Which of these is a counterexample to the following statement?

If a number is divisible by 3 then it is odd.

• 3

• 6

• 8

• 11

Tags

CCSS.6.EE.B.5

Which of these is a counterexample to the following statement?

If I am not at school then I am on summer break.

• Any day in June

• Today!

• Saturdays!

• The first day of school!

Tags

CCSS.HSS.CP.A.5