Question

reasoning katie says she is thinking of two numbers whose product is 0. john claims that he knows one number for certain. is he right? how does he know?

Explanation:

This relies on the zero product property, which states that if the product of two numbers is 0, at least one of the numbers must be 0. John is right because this mathematical rule guarantees one of the two numbers has to be 0.

Answer:

Yes, John is right. He knows this because of the zero product property: for any two numbers $a$ and $b$, if $a \times b = 0$, then either $a=0$, $b=0$, or both are 0. This means at least one of the two numbers Katie is thinking of must be 0.