The sum of $3.776 + 1.64$ is:

$3.776 + 1.64 = 5.416$

Would you like any details or have any questions?

Here are 5 related questions you might find interesting:

1. What is $5.416 - 1.64$?
2. How would you add $3.776$ and $1.64$ using decimal alignment?
3. Can you multiply $3.776$ by $1.64$?
4. What is the square of $5.416$?
5. How would you round $5.416$ to the nearest whole number?

Tip: When adding decimals, align the decimal points to ensure accuracy.