If p < q and p < r, is (p)(q)(r) < p?
(1) pq < 0
(2) pr < 0
The question tells us that p < q and p < r and then asks whether the product pqr is less than p.
Statement (1) INSUFFICIENT: We learn from this statement that either p or q is negative, but since we know from the question that p < q, p must be negative. To determine whether pqr < p, let's test values for p, q, and r. Our test values must meet only 2 conditions: p must be negative and q must be positive.
I follow the explanation up to this point because next, the solution tests values, and this is where I get confused. You assign both -10 and 10 to the value r. But doesn't the parameter above state that p is less than r? So if you assign p = to -2, r cannot be -10.