The sum of $1 + 1$ is $2$.

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Here are five related questions to expand your understanding:

1. What is $2 + 2$?
2. What is $1 + 2 + 3$?
3. What is the sum of $10 + 5$?
4. How do you solve $5 - 3$?
5. What is the sum of $100 + 200$?

Tip: In mathematics, addition is a fundamental operation that combines two numbers into a single sum.