When Sarah was 6 months old, she was 21 inches tall and her head was a diameter of 4.5 inches. Now at 20 years old, she is 6 ft. 1 in. tall and her head is a diameter of 7.65 inches. If Sarah is typic

When Sarah was 6 months old, she was 21 inches tall and her head was a diameter of 4.5 inches. Now at 20 years old, she is 6 ft. 1 in. tall and her head is a diameter of 7.65 inches. If Sarah is typical, should a person at 20 years of age be considered similar to herself at 6 months of age? Please show your work and include the rationale behind your answer. 

If Sarah were taller or shorter either at 6 months of age or 20 years of age, would this make her more or less "similar" at those two ages. Justify your answer.