Final answer:
The observation of Evan's mother's small hand both pleases him and makes him sad because it symbolizes the passage of time and growing up.
Step-by-step explanation:
The reason why Evan's observation of his mother's small hand both pleased him and made him sad is because it symbolizes the passage of time and the inevitability of growing up.
In this particular passage from 'Winter Dreams' by F. Scott Fitzgerald, Evan is becoming more aware of the differences between himself and his mother. His larger hand compared to his mother's small hand indicates that he is growing older and gaining independence. This observation pleases him because it represents his growth and maturity.
However, it also makes him sad because it reminds him that he is leaving behind his childhood and entering into adulthood.