Convert the measurement to inches: 1 yard = 36 inches; 36 inches × 3 = 108 inches. Divide the total number of inches by the number of dresses being trimmed to determine the length of each piece of ribbon: 108 inches ÷ 4 = 27 inches. Convert the quotient (27 inches) to a fraction of a yard: 27/36 = 27 ÷ 36 = 75% = 3/4 of a yard.