Final answer:
To estimate the sum, round 11.91 up to 12 and 19.99 up to 20. Adding the rounded numbers gives an approximate sum of 32, demonstrating the importance of precision in mathematical operations.
Step-by-step explanation:
To estimate the sum of 11.91 and 19.99 by rounding each value to the nearest whole number, we first round 11.91 to 12 and 19.99 to 20. Then, we add the rounded numbers together. The estimated sum of the two original numbers is approximately 32.
When performing mathematical operations involving significant figures, it's important to follow rules such as:
- In addition and subtraction, the answer should have the same number of decimal places as the least precise term.
- In multiplication and division, the answer should match the least number of significant figures from the numbers used in the operation.
These rules ensure that the final answer reflects the precision of the original data.