Furthermore, small-scale classroom studies have also yielded consistent results with large-scale researches. Bragg & Outhred (2000) conducted a research study with 120 students from grades 1 – 5 to investigate students’ knowledge of length measurement. They observed that most of the students used procedural strategies (e.g. counting units and/or marks) to measure length with a ruler. Although many of the students could measure and draw lines correctly by grade 5, they failed to complete the tasks accurately which required the understanding of scale (e.g. the concept of zero point). The results also indicated that a small number of students could use informal units to construct a ruler and understand the meaning of numerals on a ruler. In addition to children’ misconceptions about a ruler, a significant number of students in the age group of 9 – 13 years could not conceptualize that while making iterations with a unit, the quantity being measured must be covered without overlaps or gaps (Hiebert, 1981). As far as the concept of perimeter concerned, Tan-Sisman & Aksu (2009) reported that most of the seventh grade students confused not only the concept of perimeter with the concept of area but also confused the formula for perimeter with area. They also found that many students have difficulties in units of length and area measurement. Similarly, Kidman & Cooper (1997) found that most of the middle grade students were good at area and perimeter questions that call for use of formula, yet they confused the area concept with the concept of perimeter.