Class 1, Grade 3 is a quick calculation method. Clever calculation is to correct some complicated geometric or mathematical problems at the fastest speed in order to find the law. This algorithm is a clever calculation, referred to as bridge calculation. Class 1, Grade 3 is a quick calculation method. Clever calculation is to correct some complicated geometric or mathematical problems at the fastest speed in order to find the law. This algorithm is a clever calculation, referred to as bridge calculation.