The sum of 2.31 and 2.075 is:

$2.31 + 2.075 = 4.385$

Would you like more details or have any questions?

Here are some related questions to expand on this concept:

1. How do you handle decimal addition with different numbers of decimal places?
2. Can you explain how to convert decimals to fractions for addition?
3. How do rounding rules affect the result of decimal addition?
4. What are some tips for estimating sums involving decimals?
5. How does adding decimals differ from adding whole numbers?

Tip: Always align decimal points vertically when performing manual addition of decimal numbers.