Open Middle®
Directions: Using the integers -9 to 9 at most one time each, place an integer in each box to make two products: one where the product is positive and one where the product is negative. You may reuse all the integers for each product.
Hint
How do we know when the product will be positive/negative? How can we tell if the value of one of the integers matters? What exceptions are there to this?
Answer
There are many answers including -5 x 4 for a negative product and 5 x 4 for a positive product.
Source: Robert Kaplinsky in Open Middle Math
this should be 6th grade.