Learning goals: Teacher Facing Calculate the percent error, correct amount, or erroneous amount, given the other two of these three quantities, and explain (orally and using other representations) the solution method. Compare and contrast (orally) strategies used for solving problems about percent error with strategies used for solving problems about percent increase or decrease. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from 7.4 Proportional Relationships and Percentages, Grade 7.