You are a medical assistant in a pediatrician’s office and one of your responsibilities is evaluating the growth of newborns and infants. Your first patient, a baby girl named Ivy Smith, was 21.5 inches long at
3 months old. At 8 months, you measure her at 24 inches long.

1. Assuming Ivy’s growth is linear, find a linear model for her growth (in inches) over time (in
months).

2. Use your model to determine how long Ivy was at birth? Explain how you know your answer is
correct, assuming this model.

3. Use your model to determine approximately how tall Ivy will be at 1 year old. At 3 years old.
Show how you know your answers are correct.

4. Use your model to estimate how old Ivy will be (in years and months) when she measures at 48
inches. Show how you know your estimate is accurate.