Question

Sally made the conjecture that the sum of any two prime numbers is a prime number.



Which equation is a counterexample to her conjecture?



A.


15 + 4 = 19


B.


2 + 11 = 13


C.


3 + 11 = 14


D.


2 + 5 = 7

Answer 1

@Ghhhostt

Answer 2

can anyof yall help

Answer 3

Which one of the answers is not a prime number?

Answer 4

A

Answer 5

A and D

Answer 6

prime numbers are numbers that i think cannot be divided by another number other than one so just look through those

Answer 7

A and D

Answer 8

Prime numbers are numbers that are divisible by the number itself and the number 1.

Prime numbers go on forever, but here is a list of prime numbers up to 20: 2, 3, 5, 7,11,13,17,19

So we are looking for an answer that makes the conjecture not true.

Looking at the first answer, we see that when we add two prime numbers we get a number that is not on our list of prime numbers. So this answer shows that the conjecture is not true. This answer is the correct answer.

Looking at the other answers, we see that when we add two prime numbers we get a prime number. So this answer doesn't show the conjecture is not true. So this answer is no good.

The third answer again shows that when we add two prime numbers we get another prime number. So this answer doesn't show the conjecture is not true. So this answer is no good.

The final answer adds a prime number and a composite number. But the conjecture says we must add two prime numbers. So this answer is no good.

So the answer C is correct.

Answer 9

csomeone medal @Ghhhostt and @matlee

Answer 10

doesnt the question say that all number have to be prime?

Answer 11

i thought it was D

Answer 12

A because a counter example is something that is the opposite and 15 is not a prime number

Answer 13

oh yeah counter example

Answer 14

Lol im glad you all are so quick >.< My website keeps freezing randomly.

Answer 15

so i am confused A C or D

Answer 16

I would say C

Answer 17

i agree with A

Answer 18

lol this is more complicated than i thought

Answer 19

Sally made the conjecture that the sum of any two prime numbers is a prime number.



Which equation is a counterexample to her conjecture?



A.


15 + 4 = 19


B.


2 + 11 = 13


C.


3 + 11 = 14


D.


2 + 5 = 7

Answer 20

A or C

Answer 21

Ayyyyyy

Answer 22

The problem with A being an example is that it's not a counter. 4 is not a prime number so it's cannot fit. I say C

Answer 23

nvm it is C

Answer 24

Definition of COUNTEREXAMPLE. : an example that refutes or disproves a proposition or theory.

Answer 25

matlee aren't you a human calculator

Answer 26

^_^

Answer 27

Yes but these are words!

Answer 28

:(

Answer 29

Yep. Its C for sure.

Answer 30

ahahha he's got a point

Answer 31

-pulls out glossary for math class

Answer 32

you can use a calculator

Answer 33

The answer is C

Answer 34

Yes, it's C for sure. They're trying to be sneaky and put that 4 into the eq.

Answer 35

Knew it all along :D

Answer 36

C it is!

Answer 37

ok stay so i can tell if it was right

Answer 38

Ok

Answer 39

AWESOME you were right C

Answer 40

KNEW IT

Answer 41

Yay I happy 4 you. Good work! :D

Answer 42

thanks

Answer 43

Good job Denisha

Answer 44

yes

Answer 45

Lol I was about to ask how you know my name and then I looked up at my user xD