To calculate the score for a baby that is 18 inches long, we can see how far this measurement is from the 20-inch reference point.
The difference between 18 inches and 20 inches is: 20 - 18 = 2 inches
This means that the baby is 2 inches shorter than the reference point. Since scores decrease for lengths below 20 inches, we will need to assign a negative score.
From the previous examples, it appears that for each inch below 20 inches, the score decreases by a certain number. In the case of a baby at 16 inches, the score is -4, which means there is a decrease of 2 points for each inch below 20 inches (since the baby is 4 inches shorter, translating to -4).
Given that 18 inches is 2 inches shorter than 20 inches, we can calculate the score as follows:
- Score for 16 inches = -4 (which is 4 points for being 4 inches shorter)
- Since 18 inches is 2 inches shorter than 20 inches:
- Score for 18 inches = -4 + 2 = -2.
Thus, the baby that is 18 inches long receives a score of -2.
The final answer is: -2