On the other hand, Chan's knowledge about the nature and discourse of perimeter and area was also limited. Chan was concerned with 'getting an answer' without checking the reasonableness of his answers. Thus, he made careless mistakes in calculating the area of composite figure in Tasks 12. These mistakes could be avoided if he had checked the reasonableness of his answers. Chan had literally read 6 m2 as '6 meters squared' instead of '6 square meters'. Therefore, it can be concluded that Chan had inadequate SMK of perimeter and area that he is going to teach.