Which star-marked tooth number is closest to 20?

Which star-marked tooth number is closest to 20?

• A. 18
• B. 20
• C. 31
• D. 4

Answer: (B)

Distance between numbers on the universal tooth-numbering scale is what this item checks. Each adult tooth has a unique number from 1 to 32, and closeness is measured by the absolute difference between numbers. If the star-marked tooth has the same number as the target, the distance is zero—the smallest possible distance—so it is the closest. In this diagram, the star-marked tooth is numbered 20, which makes it exactly at the target with zero distance. Any other numbered tooth would be farther away on the number line.

Distance between numbers on the universal tooth-numbering scale is what this item checks. Each adult tooth has a unique number from 1 to 32, and closeness is measured by the absolute difference between numbers. If the star-marked tooth has the same number as the target, the distance is zero—the smallest possible distance—so it is the closest. In this diagram, the star-marked tooth is numbered 20, which makes it exactly at the target with zero distance. Any other numbered tooth would be farther away on the number line.