Métodos de Cálculo de Porcentagem: Regra de Três, Fração e Decimais

Section role: supports the 'Desvendando Problemas de Porcentagem' section while the teacher demonstrates the three calculation methods on the board and addresses common pitfalls like direct subtraction errors. Slides: (1) Title — 'Desvendando Problemas de Porcentagem'; (2) O Problema do Tênis — bullets: example of a R$ 200,00 sneaker with a 15% discount, calculating how much is saved; (3) Método 1: Fração Centesimal — bullets: converting 15% to 15/100, multiplying by 200, step-by-step resolution; (4) Método 2: Forma Decimal — bullets: converting 15% to 0,20 or 0,15, multiplying by 200, algebraic simplicity; (5) Método 3: Regra de Três — bullets: setting up the table with total 200 equal to 100%, finding x for 15%; (6) Alerta de Erro Comum — bullets: why doing 200 - 15 is wrong, highlighting the necessity of calculating the percentage of the specific base value first; (7) Acréscimo e Desconto — bullets: conceptual question 'Se algo aumenta 10%, o novo valor será maior ou menor que 100%?', introducing increases and decreases; (8) Aplicação Prática — bullets: working through the runner-up example or the 40 students room challenge to set up the practice phase. Closing slide: 'Qual dos três métodos você achou mais fácil de aplicar e por quê?' — sets up the 'Mão na Massa' section that follows.