The sum of $21 + 16$ is $37$.

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Here are 5 related questions:

1. What is the result of $37 + 25$?
2. Can you find the sum of $50 + 18$?
3. What is $100 - 37$?
4. How much is $21 \times 16$?
5. What is the difference between $21$ and $16$?

Tip: Addition is one of the most fundamental arithmetic operations. Practicing it helps improve mental math skills!