Question

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

Which equation is a counterexample to his conjecture?

A.
17 + 2 = 19

B.
11 + 5 = 16

C.
3 + 10 = 13

D.
4 + 1 = 5

Answer 1

plz help

Answer 2

You can rule out C and D because they both include numbers that aren't prime. If he wants to find the sum of two prime numbers, then he can't include 4 or 10 as one of the numbers being added (both divisible by 2, meaning they're not prime).

So now look at A and B. They both add prime numbers, which is what this problem wants. Harold says their sum (answer) should be a composite number (not prime; meaning it's divisible by something other than 1). To find a COUNTEREXAMPLE of that, we need to pick the problem that adds two prime numbers and gets another prime number as an answer.

So the two answers we have to choose from are A. 19 or B. 16... Which one of those is prime? That's your answer.

Answer 3

thx dude

Answer 4

it was a

Answer 5

Great job! You're welcome! :)

Answer 6

dude i have one more

Answer 7

are you still there