Fractions require a consistent unit whole

Two learners describe paper strips that began as identical wholes. One strip is divided into four equal parts and two are shaded. The other is divided into eight equal parts and four are shaded. A learner says four eighths must be larger because four is greater than two. Another compares the shaded regions after lining up the equal wholes and sees the same covered amount. The task asks for the relationship between the fractions and the meaning of the denominator. No strip has been stretched, cut from a larger original or measured with a different unit. This is a verbal model, so no unseen picture is required. The explanation should show why changing the size of the parts and their count together can preserve an amount.