Learning goals: Teacher Facing Apply operations with signed numbers to solve problems involving constant rates, and explain (orally) the solution method. Explain (orally and in writing) how signed numbers can be used to represent situations involving constant rates. Write an equation of the form $y=\text-kx$ to represent a situation that involves descending at a constant rate. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from 7.5 Rational Number Arithmetic, Grade 7.